user_guide/libraries/encryption.html


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405


<!DOCTYPE html>
<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]-->
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  
  <title>Encryption Library &mdash; CodeIgniter 3.1.7 documentation</title>
  

    <link rel="shortcut icon" href="../_static/ci-icon.ico"/>
  

  <link href='https://fonts.googleapis.com/css?family=Lato:400,700,400italic,700italic|Roboto+Slab:400,700|Inconsolata:400,700&subset=latin,cyrillic' rel='stylesheet' type='text/css'>

  
    <link rel="stylesheet" href="../_static/css/citheme.css" type="text/css" />
  

        <link rel="index" title="Index"
              href="../genindex.html"/>
        <link rel="search" title="Search" href="../search.html"/>
    <link rel="top" title="CodeIgniter 3.1.7 documentation" href="../index.html"/>
        <link rel="up" title="Libraries" href="index.html"/>
        <link rel="next" title="File Uploading Class" href="file_uploading.html"/>
        <link rel="prev" title="Encrypt Class" href="encrypt.html"/> 

  
  <script src="https://cdnjs.cloudflare.com/ajax/libs/modernizr/2.6.2/modernizr.min.js"></script>

</head>

<body class="wy-body-for-nav" role="document">

  <div id="nav">
  <div id="nav_inner">
    
    
      <div id="pulldown-menu" class="ciNav">
        <ul>
<li class="toctree-l1"><a class="reference internal" href="../general/welcome.html">Welcome to CodeIgniter</a></li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../installation/index.html">Installation Instructions</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../installation/downloads.html">Downloading CodeIgniter</a></li>
<li class="toctree-l2"><a class="reference internal" href="../installation/index.html">Installation Instructions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../installation/upgrading.html">Upgrading From a Previous Version</a></li>
<li class="toctree-l2"><a class="reference internal" href="../installation/troubleshooting.html">Troubleshooting</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../overview/index.html">CodeIgniter Overview</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../overview/getting_started.html">Getting Started</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/at_a_glance.html">CodeIgniter at a Glance</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/features.html">Supported Features</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/appflow.html">Application Flow Chart</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/mvc.html">Model-View-Controller</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/goals.html">Architectural Goals</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../tutorial/index.html">Tutorial</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../tutorial/static_pages.html">Static pages</a></li>
<li class="toctree-l2"><a class="reference internal" href="../tutorial/news_section.html">News section</a></li>
<li class="toctree-l2"><a class="reference internal" href="../tutorial/create_news_items.html">Create news items</a></li>
<li class="toctree-l2"><a class="reference internal" href="../tutorial/conclusion.html">Conclusion</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../contributing/index.html">Contributing to CodeIgniter</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../documentation/index.html">Writing CodeIgniter Documentation</a></li>
<li class="toctree-l2"><a class="reference internal" href="../DCO.html">Developer’s Certificate of Origin 1.1</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../general/index.html">General Topics</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../general/urls.html">CodeIgniter URLs</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/controllers.html">Controllers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/reserved_names.html">Reserved Names</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/views.html">Views</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/models.html">Models</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/helpers.html">Helpers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/libraries.html">Using CodeIgniter Libraries</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/creating_libraries.html">Creating Libraries</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/drivers.html">Using CodeIgniter Drivers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/creating_drivers.html">Creating Drivers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/core_classes.html">Creating Core System Classes</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/ancillary_classes.html">Creating Ancillary Classes</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/hooks.html">Hooks - Extending the Framework Core</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/autoloader.html">Auto-loading Resources</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/common_functions.html">Common Functions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/compatibility_functions.html">Compatibility Functions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/routing.html">URI Routing</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/errors.html">Error Handling</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/caching.html">Caching</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/profiling.html">Profiling Your Application</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/cli.html">Running via the CLI</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/managing_apps.html">Managing your Applications</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/environments.html">Handling Multiple Environments</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/alternative_php.html">Alternate PHP Syntax for View Files</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/security.html">Security</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/styleguide.html">PHP Style Guide</a></li>
</ul>
</li>
</ul>
<ul class="current">
<li class="toctree-l1 current"><a class="reference internal" href="index.html">Libraries</a><ul class="current">
<li class="toctree-l2"><a class="reference internal" href="benchmark.html">Benchmarking Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="caching.html">Caching Driver</a></li>
<li class="toctree-l2"><a class="reference internal" href="calendar.html">Calendaring Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="cart.html">Shopping Cart Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="config.html">Config Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="email.html">Email Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="encrypt.html">Encrypt Class</a></li>
<li class="toctree-l2 current"><a class="current reference internal" href="#">Encryption Library</a></li>
<li class="toctree-l2"><a class="reference internal" href="file_uploading.html">File Uploading Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="form_validation.html">Form Validation</a></li>
<li class="toctree-l2"><a class="reference internal" href="ftp.html">FTP Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="image_lib.html">Image Manipulation Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="input.html">Input Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="javascript.html">Javascript Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="language.html">Language Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="loader.html">Loader Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="migration.html">Migrations Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="output.html">Output Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="pagination.html">Pagination Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="parser.html">Template Parser Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="security.html">Security Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="sessions.html">Session Library</a></li>
<li class="toctree-l2"><a class="reference internal" href="table.html">HTML Table Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="trackback.html">Trackback Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="typography.html">Typography Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="unit_testing.html">Unit Testing Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="uri.html">URI Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="user_agent.html">User Agent Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="xmlrpc.html">XML-RPC and XML-RPC Server Classes</a></li>
<li class="toctree-l2"><a class="reference internal" href="zip.html">Zip Encoding Class</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../database/index.html">Database Reference</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../database/examples.html">Quick Start: Usage Examples</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/configuration.html">Database Configuration</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/connecting.html">Connecting to a Database</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/queries.html">Running Queries</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/results.html">Generating Query Results</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/helpers.html">Query Helper Functions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/query_builder.html">Query Builder Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/transactions.html">Transactions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/metadata.html">Getting MetaData</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/call_function.html">Custom Function Calls</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/caching.html">Query Caching</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/forge.html">Database Manipulation with Database Forge</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/utilities.html">Database Utilities Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/db_driver_reference.html">Database Driver Reference</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../helpers/index.html">Helpers</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../helpers/array_helper.html">Array Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/captcha_helper.html">CAPTCHA Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/cookie_helper.html">Cookie Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/date_helper.html">Date Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/directory_helper.html">Directory Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/download_helper.html">Download Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/email_helper.html">Email Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/file_helper.html">File Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/form_helper.html">Form Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/html_helper.html">HTML Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/inflector_helper.html">Inflector Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/language_helper.html">Language Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/number_helper.html">Number Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/path_helper.html">Path Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/security_helper.html">Security Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/smiley_helper.html">Smiley Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/string_helper.html">String Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/text_helper.html">Text Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/typography_helper.html">Typography Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/url_helper.html">URL Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/xml_helper.html">XML Helper</a></li>
</ul>
</li>
</ul>

      </div>
    
      
  </div>
</div>
<div id="nav2">
  <a href="#" id="openToc">
    <img src="data:image/jpeg;base64,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" title="Toggle Table of Contents" alt="Toggle Table of Contents" />
  </a>
</div>

  <div class="wy-grid-for-nav">

    
    <nav data-toggle="wy-nav-shift" class="wy-nav-side">
      <div class="wy-side-nav-search">
        
          <a href="../index.html" class="fa fa-home"> CodeIgniter</a>
        
        
<div role="search">
  <form id="rtd-search-form" class="wy-form" action="../search.html" method="get">
    <input type="text" name="q" placeholder="Search docs" />
    <input type="hidden" name="check_keywords" value="yes" />
    <input type="hidden" name="area" value="default" />
  </form>
</div>
      </div>

      <div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
        
          
              <ul>
<li class="toctree-l1"><a class="reference internal" href="../general/welcome.html">Welcome to CodeIgniter</a></li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../installation/index.html">Installation Instructions</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../installation/downloads.html">Downloading CodeIgniter</a></li>
<li class="toctree-l2"><a class="reference internal" href="../installation/index.html">Installation Instructions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../installation/upgrading.html">Upgrading From a Previous Version</a></li>
<li class="toctree-l2"><a class="reference internal" href="../installation/troubleshooting.html">Troubleshooting</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../overview/index.html">CodeIgniter Overview</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../overview/getting_started.html">Getting Started</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/at_a_glance.html">CodeIgniter at a Glance</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/features.html">Supported Features</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/appflow.html">Application Flow Chart</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/mvc.html">Model-View-Controller</a></li>
<li class="toctree-l2"><a class="reference internal" href="../overview/goals.html">Architectural Goals</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../tutorial/index.html">Tutorial</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../tutorial/static_pages.html">Static pages</a></li>
<li class="toctree-l2"><a class="reference internal" href="../tutorial/news_section.html">News section</a></li>
<li class="toctree-l2"><a class="reference internal" href="../tutorial/create_news_items.html">Create news items</a></li>
<li class="toctree-l2"><a class="reference internal" href="../tutorial/conclusion.html">Conclusion</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../contributing/index.html">Contributing to CodeIgniter</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../documentation/index.html">Writing CodeIgniter Documentation</a></li>
<li class="toctree-l2"><a class="reference internal" href="../DCO.html">Developer’s Certificate of Origin 1.1</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../general/index.html">General Topics</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../general/urls.html">CodeIgniter URLs</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/controllers.html">Controllers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/reserved_names.html">Reserved Names</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/views.html">Views</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/models.html">Models</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/helpers.html">Helpers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/libraries.html">Using CodeIgniter Libraries</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/creating_libraries.html">Creating Libraries</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/drivers.html">Using CodeIgniter Drivers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/creating_drivers.html">Creating Drivers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/core_classes.html">Creating Core System Classes</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/ancillary_classes.html">Creating Ancillary Classes</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/hooks.html">Hooks - Extending the Framework Core</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/autoloader.html">Auto-loading Resources</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/common_functions.html">Common Functions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/compatibility_functions.html">Compatibility Functions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/routing.html">URI Routing</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/errors.html">Error Handling</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/caching.html">Caching</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/profiling.html">Profiling Your Application</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/cli.html">Running via the CLI</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/managing_apps.html">Managing your Applications</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/environments.html">Handling Multiple Environments</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/alternative_php.html">Alternate PHP Syntax for View Files</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/security.html">Security</a></li>
<li class="toctree-l2"><a class="reference internal" href="../general/styleguide.html">PHP Style Guide</a></li>
</ul>
</li>
</ul>
<ul class="current">
<li class="toctree-l1 current"><a class="reference internal" href="index.html">Libraries</a><ul class="current">
<li class="toctree-l2"><a class="reference internal" href="benchmark.html">Benchmarking Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="caching.html">Caching Driver</a></li>
<li class="toctree-l2"><a class="reference internal" href="calendar.html">Calendaring Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="cart.html">Shopping Cart Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="config.html">Config Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="email.html">Email Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="encrypt.html">Encrypt Class</a></li>
<li class="toctree-l2 current"><a class="current reference internal" href="#">Encryption Library</a></li>
<li class="toctree-l2"><a class="reference internal" href="file_uploading.html">File Uploading Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="form_validation.html">Form Validation</a></li>
<li class="toctree-l2"><a class="reference internal" href="ftp.html">FTP Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="image_lib.html">Image Manipulation Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="input.html">Input Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="javascript.html">Javascript Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="language.html">Language Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="loader.html">Loader Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="migration.html">Migrations Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="output.html">Output Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="pagination.html">Pagination Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="parser.html">Template Parser Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="security.html">Security Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="sessions.html">Session Library</a></li>
<li class="toctree-l2"><a class="reference internal" href="table.html">HTML Table Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="trackback.html">Trackback Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="typography.html">Typography Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="unit_testing.html">Unit Testing Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="uri.html">URI Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="user_agent.html">User Agent Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="xmlrpc.html">XML-RPC and XML-RPC Server Classes</a></li>
<li class="toctree-l2"><a class="reference internal" href="zip.html">Zip Encoding Class</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../database/index.html">Database Reference</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../database/examples.html">Quick Start: Usage Examples</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/configuration.html">Database Configuration</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/connecting.html">Connecting to a Database</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/queries.html">Running Queries</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/results.html">Generating Query Results</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/helpers.html">Query Helper Functions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/query_builder.html">Query Builder Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/transactions.html">Transactions</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/metadata.html">Getting MetaData</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/call_function.html">Custom Function Calls</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/caching.html">Query Caching</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/forge.html">Database Manipulation with Database Forge</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/utilities.html">Database Utilities Class</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/db_driver_reference.html">Database Driver Reference</a></li>
</ul>
</li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../helpers/index.html">Helpers</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../helpers/array_helper.html">Array Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/captcha_helper.html">CAPTCHA Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/cookie_helper.html">Cookie Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/date_helper.html">Date Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/directory_helper.html">Directory Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/download_helper.html">Download Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/email_helper.html">Email Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/file_helper.html">File Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/form_helper.html">Form Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/html_helper.html">HTML Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/inflector_helper.html">Inflector Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/language_helper.html">Language Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/number_helper.html">Number Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/path_helper.html">Path Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/security_helper.html">Security Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/smiley_helper.html">Smiley Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/string_helper.html">String Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/text_helper.html">Text Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/typography_helper.html">Typography Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/url_helper.html">URL Helper</a></li>
<li class="toctree-l2"><a class="reference internal" href="../helpers/xml_helper.html">XML Helper</a></li>
</ul>
</li>
</ul>

          
      </div>
      &nbsp;
    </nav>

    <section data-toggle="wy-nav-shift" class="wy-nav-content-wrap">

      
      <nav class="wy-nav-top" role="navigation" aria-label="top navigation">
        <i data-toggle="wy-nav-top" class="fa fa-bars"></i>
        <a href="../index.html">CodeIgniter</a>
      </nav>


      <div class="wy-nav-content">
        <div class="rst-content">
          <div role="navigation" aria-label="breadcrumbs navigation">
  <ul class="wy-breadcrumbs">
    <li><a href="../index.html">Docs</a> &raquo;</li>
      
        <li><a href="index.html">Libraries</a> &raquo;</li>
      
    <li>Encryption Library</li>
    <li class="wy-breadcrumbs-aside">
      
    </li>
    <div style="float:right;margin-left:5px;" id="closeMe">
      <img title="Classic Layout" alt="classic layout" src="data:image/gif;base64,R0lGODlhFAAUAJEAAAAAADMzM////wAAACH5BAUUAAIALAAAAAAUABQAAAImlI+py+0PU5gRBRDM3DxbWoXis42X13USOLauUIqnlsaH/eY6UwAAOw==" />
    </div>
  </ul>
  <hr/>
</div>
          <div role="main" class="document">
            
  <div class="section" id="encryption-library">
<h1>Encryption Library<a class="headerlink" href="#encryption-library" title="Permalink to this headline">¶</a></h1>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">DO NOT use this or any other <em>encryption</em> library for
user password storage! Passwords must be <em>hashed</em> instead, and you
should do that via PHP’s own <a class="reference external" href="http://php.net/password">Password Hashing extension</a>.</p>
</div>
<p>The Encryption Library provides two-way data encryption. To do so in
a cryptographically secure way, it utilizes PHP extensions that are
unfortunately not always available on all systems.
You must meet one of the following dependencies in order to use this
library:</p>
<ul class="simple">
<li><a class="reference external" href="http://php.net/openssl">OpenSSL</a></li>
<li><a class="reference external" href="http://php.net/mcrypt">MCrypt</a> (and <cite>MCRYPT_DEV_URANDOM</cite> availability)</li>
</ul>
<p>If neither of the above dependencies is met, we simply cannot offer
you a good enough implementation to meet the high standards required
for proper cryptography.</p>
<div class="contents local topic" id="contents">
<ul class="simple">
<li><a class="reference internal" href="#using-the-encryption-library" id="id2">Using the Encryption Library</a><ul>
<li><a class="reference internal" href="#initializing-the-class" id="id3">Initializing the Class</a></li>
<li><a class="reference internal" href="#default-behavior" id="id4">Default behavior</a></li>
<li><a class="reference internal" href="#setting-your-encryption-key" id="id5">Setting your encryption_key</a></li>
<li><a class="reference internal" href="#supported-encryption-ciphers-and-modes" id="id6">Supported encryption ciphers and modes</a><ul>
<li><a class="reference internal" href="#portable-ciphers" id="id7">Portable ciphers</a></li>
<li><a class="reference internal" href="#driver-specific-ciphers" id="id8">Driver-specific ciphers</a></li>
<li><a class="reference internal" href="#encryption-modes" id="id9">Encryption modes</a></li>
</ul>
</li>
<li><a class="reference internal" href="#message-length" id="id10">Message Length</a></li>
<li><a class="reference internal" href="#configuring-the-library" id="id11">Configuring the library</a></li>
<li><a class="reference internal" href="#encrypting-and-decrypting-data" id="id12">Encrypting and decrypting data</a><ul>
<li><a class="reference internal" href="#how-it-works" id="id13">How it works</a></li>
<li><a class="reference internal" href="#using-custom-parameters" id="id14">Using custom parameters</a></li>
<li><a class="reference internal" href="#supported-hmac-authentication-algorithms" id="id15">Supported HMAC authentication algorithms</a></li>
</ul>
</li>
</ul>
</li>
<li><a class="reference internal" href="#class-reference" id="id16">Class Reference</a></li>
</ul>
</div>
<div class="custom-index container"></div><div class="section" id="using-the-encryption-library">
<h2><a class="toc-backref" href="#id2">Using the Encryption Library</a><a class="headerlink" href="#using-the-encryption-library" title="Permalink to this headline">¶</a></h2>
<div class="section" id="initializing-the-class">
<h3><a class="toc-backref" href="#id3">Initializing the Class</a><a class="headerlink" href="#initializing-the-class" title="Permalink to this headline">¶</a></h3>
<p>Like most other classes in CodeIgniter, the Encryption library is
initialized in your controller using the <code class="docutils literal"><span class="pre">$this-&gt;load-&gt;library()</span></code>
method:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">load</span><span class="o">-&gt;</span><span class="na">library</span><span class="p">(</span><span class="s1">&#39;encryption&#39;</span><span class="p">);</span>
</pre></div>
</div>
<p>Once loaded, the Encryption library object will be available using:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span>
</pre></div>
</div>
</div>
<div class="section" id="default-behavior">
<h3><a class="toc-backref" href="#id4">Default behavior</a><a class="headerlink" href="#default-behavior" title="Permalink to this headline">¶</a></h3>
<p>By default, the Encryption Library will use the AES-128 cipher in CBC
mode, using your configured <em>encryption_key</em> and SHA512 HMAC authentication.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">AES-128 is chosen both because it is proven to be strong and
because of its wide availability across different cryptographic
software and programming languages’ APIs.</p>
</div>
<p>However, the <em>encryption_key</em> is not used as is.</p>
<p>If you are somewhat familiar with cryptography, you should already know
that a HMAC also requires a secret key and using the same key for both
encryption and authentication is a bad practice.</p>
<p>Because of that, two separate keys are derived from your already configured
<em>encryption_key</em>: one for encryption and one for authentication. This is
done via a technique called <a class="reference external" href="http://en.wikipedia.org/wiki/HKDF">HMAC-based Key Derivation Function</a> (HKDF).</p>
</div>
<div class="section" id="setting-your-encryption-key">
<h3><a class="toc-backref" href="#id5">Setting your encryption_key</a><a class="headerlink" href="#setting-your-encryption-key" title="Permalink to this headline">¶</a></h3>
<p>An <em>encryption key</em> is a piece of information that controls the
cryptographic process and permits a plain-text string to be encrypted,
and afterwards - decrypted. It is the secret “ingredient” in the whole
process that allows you to be the only one who is able to decrypt data
that you’ve decided to hide from the eyes of the public.
After one key is used to encrypt data, that same key provides the <strong>only</strong>
means to decrypt it, so not only must you chose one carefully, but you
must not lose it or you will also lose access to the data.</p>
<p>It must be noted that to ensure maximum security, such key <em>should</em> not
only be as strong as possible, but also often changed. Such behavior
however is rarely practical or possible to implement, and that is why
CodeIgniter gives you the ability to configure a single key that is to be
used (almost) every time.</p>
<p>It goes without saying that you should guard your key carefully. Should
someone gain access to your key, the data will be easily decrypted. If
your server is not totally under your control it’s impossible to ensure
key security so you may want to think carefully before using it for
anything that requires high security, like storing credit card numbers.</p>
<p>Your encryption key <strong>must</strong> be as long as the encyption algorithm in use
allows. For AES-128, that’s 128 bits or 16 bytes (charcters) long.
You will find a table below that shows the supported key lengths of
different ciphers.</p>
<p>The key should be as random as possible and it <strong>must not</strong> be a regular
text string, nor the output of a hashing function, etc. In order to create
a proper key, you must use the Encryption library’s <code class="docutils literal"><span class="pre">create_key()</span></code> method</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// $key will be assigned a 16-byte (128-bit) random key</span>
<span class="nv">$key</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">create_key</span><span class="p">(</span><span class="mi">16</span><span class="p">);</span>
</pre></div>
</div>
<p>The key can be either stored in your <em>application/config/config.php</em>, or
you can design your own storage mechanism and pass the key dynamically
when encrypting/decrypting.</p>
<p>To save your key to your <em>application/config/config.php</em>, open the file
and set:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$config</span><span class="p">[</span><span class="s1">&#39;encryption_key&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;YOUR KEY&#39;</span><span class="p">;</span>
</pre></div>
</div>
<p>You’ll notice that the <code class="docutils literal"><span class="pre">create_key()</span></code> method outputs binary data, which
is hard to deal with (i.e. a copy-paste may damage it), so you may use
<code class="docutils literal"><span class="pre">bin2hex()</span></code>, <code class="docutils literal"><span class="pre">hex2bin()</span></code> or Base64-encoding to work with the key in
a more friendly manner. For example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Get a hex-encoded representation of the key:</span>
<span class="nv">$key</span> <span class="o">=</span> <span class="nb">bin2hex</span><span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">create_key</span><span class="p">(</span><span class="mi">16</span><span class="p">));</span>

<span class="c1">// Put the same value in your config with hex2bin(),</span>
<span class="c1">// so that it is still passed as binary to the library:</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">&#39;encryption_key&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="nb">hex2bin</span><span class="p">(</span><span class="o">&lt;</span><span class="nx">your</span> <span class="nx">hex</span><span class="o">-</span><span class="nx">encoded</span> <span class="nb">key</span><span class="o">&gt;</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="section" id="supported-encryption-ciphers-and-modes">
<span id="ciphers-and-modes"></span><h3><a class="toc-backref" href="#id6">Supported encryption ciphers and modes</a><a class="headerlink" href="#supported-encryption-ciphers-and-modes" title="Permalink to this headline">¶</a></h3>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The terms ‘cipher’ and ‘encryption algorithm’ are interchangeable.</p>
</div>
<div class="section" id="portable-ciphers">
<h4><a class="toc-backref" href="#id7">Portable ciphers</a><a class="headerlink" href="#portable-ciphers" title="Permalink to this headline">¶</a></h4>
<p>Because MCrypt and OpenSSL (also called drivers throughout this document)
each support different sets of encryption algorithms and often implement
them in different ways, our Encryption library is designed to use them in
a portable fashion, or in other words - it enables you to use them
interchangeably, at least for the ciphers supported by both drivers.</p>
<p>It is also implemented in a way that aims to match the standard
implementations in other programming languages and libraries.</p>
<p>Here’s a list of the so called “portable” ciphers, where
“CodeIgniter name” is the string value that you’d have to pass to the
Encryption library to use that cipher:</p>
<table border="1" class="docutils">
<colgroup>
<col width="24%" />
<col width="18%" />
<col width="28%" />
<col width="31%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Cipher name</th>
<th class="head">CodeIgniter name</th>
<th class="head">Key lengths (bits / bytes)</th>
<th class="head">Supported modes</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>AES-128 / Rijndael-128</td>
<td>aes-128</td>
<td>128 / 16</td>
<td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
</tr>
<tr class="row-odd"><td>AES-192</td>
<td>aes-192</td>
<td>192 / 24</td>
<td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
</tr>
<tr class="row-even"><td>AES-256</td>
<td>aes-256</td>
<td>256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
</tr>
<tr class="row-odd"><td>DES</td>
<td>des</td>
<td>56 / 7</td>
<td>CBC, CFB, CFB8, OFB, ECB</td>
</tr>
<tr class="row-even"><td>TripleDES</td>
<td>tripledes</td>
<td>56 / 7, 112 / 14, 168 / 21</td>
<td>CBC, CFB, CFB8, OFB</td>
</tr>
<tr class="row-odd"><td>Blowfish</td>
<td>blowfish</td>
<td>128-448 / 16-56</td>
<td>CBC, CFB, OFB, ECB</td>
</tr>
<tr class="row-even"><td>CAST5 / CAST-128</td>
<td>cast5</td>
<td>88-128 / 11-16</td>
<td>CBC, CFB, OFB, ECB</td>
</tr>
<tr class="row-odd"><td>RC4 / ARCFour</td>
<td>rc4</td>
<td>40-2048 / 5-256</td>
<td>Stream</td>
</tr>
</tbody>
</table>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">Because of how MCrypt works, if you fail to provide a key
with the appropriate length, you might end up using a different
algorithm than the one configured, so be really careful with that!</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">In case it isn’t clear from the above table, Blowfish, CAST5
and RC4 support variable length keys. That is, any number in the
shown ranges is valid, although in bit terms that only happens
in 8-bit increments.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Even though CAST5 supports key lengths lower than 128 bits
(16 bytes), in fact they will just be zero-padded to the
maximum length, as specified in <a class="reference external" href="http://tools.ietf.org/rfc/rfc2144.txt">RFC 2144</a>.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Blowfish supports key lengths as small as 32 bits (4 bytes), but
our tests have shown that only lengths of 128 bits (16 bytes) or
higher are properly supported by both MCrypt and OpenSSL. It is
also a bad practice to use such low-length keys anyway.</p>
</div>
</div>
<div class="section" id="driver-specific-ciphers">
<h4><a class="toc-backref" href="#id8">Driver-specific ciphers</a><a class="headerlink" href="#driver-specific-ciphers" title="Permalink to this headline">¶</a></h4>
<p>As noted above, MCrypt and OpenSSL support different sets of encryption
ciphers. For portability reasons and because we haven’t tested them
properly, we do not advise you to use the ones that are driver-specific,
but regardless, here’s a list of most of them:</p>
<table border="1" class="docutils">
<colgroup>
<col width="15%" />
<col width="10%" />
<col width="32%" />
<col width="44%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Cipher name</th>
<th class="head">Driver</th>
<th class="head">Key lengths (bits / bytes)</th>
<th class="head">Supported modes</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>AES-128</td>
<td>OpenSSL</td>
<td>128 / 16</td>
<td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
</tr>
<tr class="row-odd"><td>AES-192</td>
<td>OpenSSL</td>
<td>192 / 24</td>
<td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
</tr>
<tr class="row-even"><td>AES-256</td>
<td>OpenSSL</td>
<td>256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
</tr>
<tr class="row-odd"><td>Rijndael-128</td>
<td>MCrypt</td>
<td>128 / 16, 192 / 24, 256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-even"><td>Rijndael-192</td>
<td>MCrypt</td>
<td>128 / 16, 192 / 24, 256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-odd"><td>Rijndael-256</td>
<td>MCrypt</td>
<td>128 / 16, 192 / 24, 256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-even"><td>GOST</td>
<td>MCrypt</td>
<td>256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-odd"><td>Twofish</td>
<td>MCrypt</td>
<td>128 / 16, 192 / 24, 256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-even"><td>CAST-128</td>
<td>MCrypt</td>
<td>40-128 / 5-16</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-odd"><td>CAST-256</td>
<td>MCrypt</td>
<td>128 / 16, 192 / 24, 256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-even"><td>Loki97</td>
<td>MCrypt</td>
<td>128 / 16, 192 / 24, 256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-odd"><td>SaferPlus</td>
<td>MCrypt</td>
<td>128 / 16, 192 / 24, 256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-even"><td>Serpent</td>
<td>MCrypt</td>
<td>128 / 16, 192 / 24, 256 / 32</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-odd"><td>XTEA</td>
<td>MCrypt</td>
<td>128 / 16</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-even"><td>RC2</td>
<td>MCrypt</td>
<td>8-1024 / 1-128</td>
<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
</tr>
<tr class="row-odd"><td>RC2</td>
<td>OpenSSL</td>
<td>8-1024 / 1-128</td>
<td>CBC, CFB, OFB, ECB</td>
</tr>
<tr class="row-even"><td>Camellia-128</td>
<td>OpenSSL</td>
<td>128 / 16</td>
<td>CBC, CFB, CFB8, OFB, ECB</td>
</tr>
<tr class="row-odd"><td>Camellia-192</td>
<td>OpenSSL</td>
<td>192 / 24</td>
<td>CBC, CFB, CFB8, OFB, ECB</td>
</tr>
<tr class="row-even"><td>Camellia-256</td>
<td>OpenSSL</td>
<td>256 / 32</td>
<td>CBC, CFB, CFB8, OFB, ECB</td>
</tr>
<tr class="row-odd"><td>Seed</td>
<td>OpenSSL</td>
<td>128 / 16</td>
<td>CBC, CFB, OFB, ECB</td>
</tr>
</tbody>
</table>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">If you wish to use one of those ciphers, you’d have to pass
its name in lower-case to the Encryption library.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">You’ve probably noticed that all AES cipers (and Rijndael-128)
are also listed in the portable ciphers list. This is because
drivers support different modes for these ciphers. Also, it is
important to note that AES-128 and Rijndael-128 are actually
the same cipher, but <strong>only</strong> when used with a 128-bit key.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">CAST-128 / CAST-5 is also listed in both the portable and
driver-specific ciphers list. This is because OpenSSL’s
implementation doesn’t appear to be working correctly with
key sizes of 80 bits and lower.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">RC2 is listed as supported by both MCrypt and OpenSSL.
However, both drivers implement them differently and they
are not portable. It is probably worth noting that we only
found one obscure source confirming that it is MCrypt that
is not properly implementing it.</p>
</div>
</div>
<div class="section" id="encryption-modes">
<span id="id1"></span><h4><a class="toc-backref" href="#id9">Encryption modes</a><a class="headerlink" href="#encryption-modes" title="Permalink to this headline">¶</a></h4>
<p>Different modes of encryption have different characteristics and serve
for different purposes. Some are stronger than others, some are faster
and some offer extra features.
We are not going in depth into that here, we’ll leave that to the
cryptography experts. The table below is to provide brief informational
reference to our more experienced users. If you are a beginner, just
stick to the CBC mode - it is widely accepted as strong and secure for
general purposes.</p>
<table border="1" class="docutils">
<colgroup>
<col width="6%" />
<col width="9%" />
<col width="9%" />
<col width="76%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Mode name</th>
<th class="head">CodeIgniter name</th>
<th class="head">Driver support</th>
<th class="head">Additional info</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>CBC</td>
<td>cbc</td>
<td>MCrypt, OpenSSL</td>
<td>A safe default choice</td>
</tr>
<tr class="row-odd"><td>CTR</td>
<td>ctr</td>
<td>MCrypt, OpenSSL</td>
<td>Considered as theoretically better than CBC, but not as widely available</td>
</tr>
<tr class="row-even"><td>CFB</td>
<td>cfb</td>
<td>MCrypt, OpenSSL</td>
<td>N/A</td>
</tr>
<tr class="row-odd"><td>CFB8</td>
<td>cfb8</td>
<td>MCrypt, OpenSSL</td>
<td>Same as CFB, but operates in 8-bit mode (not recommended).</td>
</tr>
<tr class="row-even"><td>OFB</td>
<td>ofb</td>
<td>MCrypt, OpenSSL</td>
<td>N/A</td>
</tr>
<tr class="row-odd"><td>OFB8</td>
<td>ofb8</td>
<td>MCrypt</td>
<td>Same as OFB, but operates in 8-bit mode (not recommended).</td>
</tr>
<tr class="row-even"><td>ECB</td>
<td>ecb</td>
<td>MCrypt, OpenSSL</td>
<td>Ignores IV (not recommended).</td>
</tr>
<tr class="row-odd"><td>XTS</td>
<td>xts</td>
<td>OpenSSL</td>
<td>Usually used for encrypting random access data such as RAM or hard-disk storage.</td>
</tr>
<tr class="row-even"><td>Stream</td>
<td>stream</td>
<td>MCrypt, OpenSSL</td>
<td>This is not actually a mode, it just says that a stream cipher is being used. Required because of the general cipher+mode initialization process.</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="message-length">
<h3><a class="toc-backref" href="#id10">Message Length</a><a class="headerlink" href="#message-length" title="Permalink to this headline">¶</a></h3>
<p>It’s probably important for you to know that an encrypted string is usually
longer than the original, plain-text string (depending on the cipher).</p>
<p>This is influenced by the cipher algorithm itself, the IV prepended to the
cipher-text and the HMAC authentication message that is also prepended.
Furthermore, the encrypted message is also Base64-encoded so that it is safe
for storage and transmission, regardless of a possible character set in use.</p>
<p>Keep this information in mind when selecting your data storage mechanism.
Cookies, for example, can only hold 4K of information.</p>
</div>
<div class="section" id="configuring-the-library">
<span id="configuration"></span><h3><a class="toc-backref" href="#id11">Configuring the library</a><a class="headerlink" href="#configuring-the-library" title="Permalink to this headline">¶</a></h3>
<p>For usability, performance, but also historical reasons tied to our old
<a class="reference internal" href="encrypt.html"><span class="doc">Encrypt Class</span></a>, the Encryption library is designed to
use repeatedly the same driver, encryption cipher, mode and key.</p>
<p>As noted in the “Default behavior” section above, this means using an
auto-detected driver (OpenSSL has a higher priority), the AES-128 ciper
in CBC mode, and your <code class="docutils literal"><span class="pre">$config['encryption_key']</span></code> value.</p>
<p>If you wish to change that however, you need to use the <code class="docutils literal"><span class="pre">initialize()</span></code>
method. It accepts an associative array of parameters, all of which are
optional:</p>
<table border="1" class="docutils">
<colgroup>
<col width="15%" />
<col width="85%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Option</th>
<th class="head">Possible values</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>driver</td>
<td>‘mcrypt’, ‘openssl’</td>
</tr>
<tr class="row-odd"><td>cipher</td>
<td>Cipher name (see <a class="reference internal" href="#ciphers-and-modes"><span class="std std-ref">Supported encryption ciphers and modes</span></a>)</td>
</tr>
<tr class="row-even"><td>mode</td>
<td>Encryption mode (see <a class="reference internal" href="#encryption-modes"><span class="std std-ref">Encryption modes</span></a>)</td>
</tr>
<tr class="row-odd"><td>key</td>
<td>Encryption key</td>
</tr>
</tbody>
</table>
<p>For example, if you were to change the encryption algorithm and
mode to AES-256 in CTR mode, this is what you should do:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span>
        <span class="k">array</span><span class="p">(</span>
                <span class="s1">&#39;cipher&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;aes-256&#39;</span><span class="p">,</span>
                <span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;ctr&#39;</span><span class="p">,</span>
                <span class="s1">&#39;key&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;&lt;a 32-character random string&gt;&#39;</span>
        <span class="p">)</span>
<span class="p">);</span>
</pre></div>
</div>
<p>Note that we only mentioned that you want to change the ciper and mode,
but we also included a key in the example. As previously noted, it is
important that you choose a key with a proper size for the used algorithm.</p>
<p>There’s also the ability to change the driver, if for some reason you
have both, but want to use MCrypt instead of OpenSSL:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Switch to the MCrypt driver</span>
<span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="s1">&#39;driver&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;mcrypt&#39;</span><span class="p">));</span>

<span class="c1">// Switch back to the OpenSSL driver</span>
<span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="s1">&#39;driver&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;openssl&#39;</span><span class="p">));</span>
</pre></div>
</div>
</div>
<div class="section" id="encrypting-and-decrypting-data">
<h3><a class="toc-backref" href="#id12">Encrypting and decrypting data</a><a class="headerlink" href="#encrypting-and-decrypting-data" title="Permalink to this headline">¶</a></h3>
<p>Encrypting and decrypting data with the already configured library
settings is simple. As simple as just passing the string to the
<code class="docutils literal"><span class="pre">encrypt()</span></code> and/or <code class="docutils literal"><span class="pre">decrypt()</span></code> methods:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$plain_text</span> <span class="o">=</span> <span class="s1">&#39;This is a plain-text message!&#39;</span><span class="p">;</span>
<span class="nv">$ciphertext</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">encrypt</span><span class="p">(</span><span class="nv">$plain_text</span><span class="p">);</span>

<span class="c1">// Outputs: This is a plain-text message!</span>
<span class="k">echo</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span><span class="nv">$ciphertext</span><span class="p">);</span>
</pre></div>
</div>
<p>And that’s it! The Encryption library will do everything necessary
for the whole process to be cryptographically secure out-of-the-box.
You don’t need to worry about it.</p>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">Both methods will return FALSE in case of an error.
While for <code class="docutils literal"><span class="pre">encrypt()</span></code> this can only mean incorrect
configuration, you should always check the return value
of <code class="docutils literal"><span class="pre">decrypt()</span></code> in production code.</p>
</div>
<div class="section" id="how-it-works">
<h4><a class="toc-backref" href="#id13">How it works</a><a class="headerlink" href="#how-it-works" title="Permalink to this headline">¶</a></h4>
<p>If you must know how the process works, here’s what happens under
the hood:</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">$this-&gt;encryption-&gt;encrypt($plain_text)</span></code><ol class="arabic">
<li>Derive an encryption key and a HMAC key from your configured
<em>encryption_key</em> via HKDF, using the SHA-512 digest algorithm.</li>
<li>Generate a random initialization vector (IV).</li>
<li>Encrypt the data via AES-128 in CBC mode (or another previously
configured cipher and mode), using the above-mentioned derived
encryption key and IV.</li>
<li>Prepend said IV to the resulting cipher-text.</li>
<li>Base64-encode the resulting string, so that it can be safely
stored or transferred without worrying about character sets.</li>
<li>Create a SHA-512 HMAC authentication message using the derived
HMAC key to ensure data integrity and prepend it to the Base64
string.</li>
</ol>
</li>
<li><code class="docutils literal"><span class="pre">$this-&gt;encryption-&gt;decrypt($ciphertext)</span></code><ol class="arabic">
<li>Derive an encryption key and a HMAC key from your configured
<em>encryption_key</em> via HKDF, using the SHA-512 digest algorithm.
Because your configured <em>encryption_key</em> is the same, this
will produce the same result as in the <code class="docutils literal"><span class="pre">encrypt()</span></code> method
above - otherwise you won’t be able to decrypt it.</li>
<li>Check if the string is long enough, separate the HMAC out of
it and validate if it is correct (this is done in a way that
prevents timing attacks against it). Return FALSE if either of
the checks fails.</li>
<li>Base64-decode the string.</li>
<li>Separate the IV out of the cipher-text and decrypt the said
cipher-text using that IV and the derived encryption key.</li>
</ol>
</li>
</ul>
</div>
<div class="section" id="using-custom-parameters">
<span id="custom-parameters"></span><h4><a class="toc-backref" href="#id14">Using custom parameters</a><a class="headerlink" href="#using-custom-parameters" title="Permalink to this headline">¶</a></h4>
<p>Let’s say you have to interact with another system that is out
of your control and uses another method to encrypt data. A
method that will most certainly not match the above-described
sequence and probably not use all of the steps either.</p>
<p>The Encryption library allows you to change how its encryption
and decryption processes work, so that you can easily tailor a
custom solution for such situations.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">It is possible to use the library in this way, without
setting an <em>encryption_key</em> in your configuration file.</p>
</div>
<p>All you have to do is to pass an associative array with a few
parameters to either the <code class="docutils literal"><span class="pre">encrypt()</span></code> or <code class="docutils literal"><span class="pre">decrypt()</span></code> method.
Here’s an example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Assume that we have $ciphertext, $key and $hmac_key</span>
<span class="c1">// from on outside source</span>

<span class="nv">$message</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span>
        <span class="nv">$ciphertext</span><span class="p">,</span>
        <span class="k">array</span><span class="p">(</span>
                <span class="s1">&#39;cipher&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;blowfish&#39;</span><span class="p">,</span>
                <span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;cbc&#39;</span><span class="p">,</span>
                <span class="s1">&#39;key&#39;</span> <span class="o">=&gt;</span> <span class="nv">$key</span><span class="p">,</span>
                <span class="s1">&#39;hmac_digest&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;sha256&#39;</span><span class="p">,</span>
                <span class="s1">&#39;hmac_key&#39;</span> <span class="o">=&gt;</span> <span class="nv">$hmac_key</span>
        <span class="p">)</span>
<span class="p">);</span>
</pre></div>
</div>
<p>In the above example, we are decrypting a message that was encrypted
using the Blowfish cipher in CBC mode and authenticated via a SHA-256
HMAC.</p>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">Note that both ‘key’ and ‘hmac_key’ are used in this
example. When using custom parameters, encryption and HMAC keys
are not derived like the default behavior of the library is.</p>
</div>
<p>Below is a list of the available options.</p>
<p>However, unless you really need to and you know what you are doing,
we advise you to not change the encryption process as this could
impact security, so please do so with caution.</p>
<table border="1" class="docutils">
<colgroup>
<col width="12%" />
<col width="14%" />
<col width="26%" />
<col width="49%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Option</th>
<th class="head">Default value</th>
<th class="head">Mandatory / Optional</th>
<th class="head">Description</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>cipher</td>
<td>N/A</td>
<td>Yes</td>
<td>Encryption algorithm (see <a class="reference internal" href="#ciphers-and-modes"><span class="std std-ref">Supported encryption ciphers and modes</span></a>).</td>
</tr>
<tr class="row-odd"><td>mode</td>
<td>N/A</td>
<td>Yes</td>
<td>Encryption mode (see <a class="reference internal" href="#encryption-modes"><span class="std std-ref">Encryption modes</span></a>).</td>
</tr>
<tr class="row-even"><td>key</td>
<td>N/A</td>
<td>Yes</td>
<td>Encryption key.</td>
</tr>
<tr class="row-odd"><td>hmac</td>
<td>TRUE</td>
<td>No</td>
<td>Whether to use a HMAC.
Boolean. If set to FALSE, then <em>hmac_digest</em> and
<em>hmac_key</em> will be ignored.</td>
</tr>
<tr class="row-even"><td>hmac_digest</td>
<td>sha512</td>
<td>No</td>
<td>HMAC message digest algorithm (see <a class="reference internal" href="#digests"><span class="std std-ref">Supported HMAC authentication algorithms</span></a>).</td>
</tr>
<tr class="row-odd"><td>hmac_key</td>
<td>N/A</td>
<td>Yes, unless <em>hmac</em> is FALSE</td>
<td>HMAC key.</td>
</tr>
<tr class="row-even"><td>raw_data</td>
<td>FALSE</td>
<td>No</td>
<td>Whether the cipher-text should be raw.
Boolean. If set to TRUE, then Base64 encoding and
decoding will not be performed and HMAC will not
be a hexadecimal string.</td>
</tr>
</tbody>
</table>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last"><code class="docutils literal"><span class="pre">encrypt()</span></code> and <code class="docutils literal"><span class="pre">decrypt()</span></code> will return FALSE if
a mandatory parameter is not provided or if a provided
value is incorrect. This includes <em>hmac_key</em>, unless <em>hmac</em>
is set to FALSE.</p>
</div>
</div>
<div class="section" id="supported-hmac-authentication-algorithms">
<span id="digests"></span><h4><a class="toc-backref" href="#id15">Supported HMAC authentication algorithms</a><a class="headerlink" href="#supported-hmac-authentication-algorithms" title="Permalink to this headline">¶</a></h4>
<p>For HMAC message authentication, the Encryption library supports
usage of the SHA-2 family of algorithms:</p>
<table border="1" class="docutils">
<colgroup>
<col width="19%" />
<col width="34%" />
<col width="47%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Algorithm</th>
<th class="head">Raw length (bytes)</th>
<th class="head">Hex-encoded length (bytes)</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>sha512</td>
<td>64</td>
<td>128</td>
</tr>
<tr class="row-odd"><td>sha384</td>
<td>48</td>
<td>96</td>
</tr>
<tr class="row-even"><td>sha256</td>
<td>32</td>
<td>64</td>
</tr>
<tr class="row-odd"><td>sha224</td>
<td>28</td>
<td>56</td>
</tr>
</tbody>
</table>
<p>The reason for not including other popular algorithms, such as
MD5 or SHA1 is that they are no longer considered secure enough
and as such, we don’t want to encourage their usage.
If you absolutely need to use them, it is easy to do so via PHP’s
native <a class="reference external" href="http://php.net/manual/en/function.hash-hmac.php">hash_hmac()</a> function.</p>
<p>Stronger algorithms of course will be added in the future as they
appear and become widely available.</p>
</div>
</div>
</div>
<div class="section" id="class-reference">
<h2><a class="toc-backref" href="#id16">Class Reference</a><a class="headerlink" href="#class-reference" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="CI_Encryption">
<em class="property">class </em><code class="descname">CI_Encryption</code><a class="headerlink" href="#CI_Encryption" title="Permalink to this definition">¶</a></dt>
<dd><dl class="method">
<dt id="CI_Encryption::initialize">
<code class="descname">initialize</code><span class="sig-paren">(</span><em>$params</em><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::initialize" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$params</strong> (<em>array</em>) – Configuration parameters</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">CI_Encryption instance (method chaining)</p>
</td>
</tr>
<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">CI_Encryption</p>
</td>
</tr>
</tbody>
</table>
<p>Initializes (configures) the library to use a different
driver, cipher, mode or key.</p>
<p>Example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span>
        <span class="k">array</span><span class="p">(</span><span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;ctr&#39;</span><span class="p">)</span>
<span class="p">);</span>
</pre></div>
</div>
<p>Please refer to the <a class="reference internal" href="#configuration"><span class="std std-ref">Configuring the library</span></a> section for detailed info.</p>
</dd></dl>

<dl class="method">
<dt id="CI_Encryption::encrypt">
<code class="descname">encrypt</code><span class="sig-paren">(</span><em>$data</em><span class="optional">[</span>, <em>$params = NULL</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::encrypt" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$data</strong> (<em>string</em>) – Data to encrypt</li>
<li><strong>$params</strong> (<em>array</em>) – Optional parameters</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">Encrypted data or FALSE on failure</p>
</td>
</tr>
<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
</td>
</tr>
</tbody>
</table>
<p>Encrypts the input data and returns its ciphertext.</p>
<p>Example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$ciphertext</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">encrypt</span><span class="p">(</span><span class="s1">&#39;My secret message&#39;</span><span class="p">);</span>
</pre></div>
</div>
<p>Please refer to the <a class="reference internal" href="#custom-parameters"><span class="std std-ref">Using custom parameters</span></a> section for information
on the optional parameters.</p>
</dd></dl>

<dl class="method">
<dt id="CI_Encryption::decrypt">
<code class="descname">decrypt</code><span class="sig-paren">(</span><em>$data</em><span class="optional">[</span>, <em>$params = NULL</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::decrypt" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$data</strong> (<em>string</em>) – Data to decrypt</li>
<li><strong>$params</strong> (<em>array</em>) – Optional parameters</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">Decrypted data or FALSE on failure</p>
</td>
</tr>
<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
</td>
</tr>
</tbody>
</table>
<p>Decrypts the input data and returns it in plain-text.</p>
<p>Example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="k">echo</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span><span class="nv">$ciphertext</span><span class="p">);</span>
</pre></div>
</div>
<p>Please refer to the <a class="reference internal" href="#custom-parameters"><span class="std std-ref">Using custom parameters</span></a> secrion for information
on the optional parameters.</p>
</dd></dl>

<dl class="method">
<dt id="CI_Encryption::create_key">
<code class="descname">create_key</code><span class="sig-paren">(</span><em>$length</em><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::create_key" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$length</strong> (<em>int</em>) – Output length</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">A pseudo-random cryptographic key with the specified length, or FALSE on failure</p>
</td>
</tr>
<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
</td>
</tr>
</tbody>
</table>
<p>Creates a cryptographic key by fetching random data from
the operating system’s sources (i.e. /dev/urandom).</p>
</dd></dl>

<dl class="method">
<dt id="CI_Encryption::hkdf">
<code class="descname">hkdf</code><span class="sig-paren">(</span><em>$key</em><span class="optional">[</span>, <em>$digest = 'sha512'</em><span class="optional">[</span>, <em>$salt = NULL</em><span class="optional">[</span>, <em>$length = NULL</em><span class="optional">[</span>, <em>$info = ''</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::hkdf" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$key</strong> (<em>string</em>) – Input key material</li>
<li><strong>$digest</strong> (<em>string</em>) – A SHA-2 family digest algorithm</li>
<li><strong>$salt</strong> (<em>string</em>) – Optional salt</li>
<li><strong>$length</strong> (<em>int</em>) – Optional output length</li>
<li><strong>$info</strong> (<em>string</em>) – Optional context/application-specific info</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">A pseudo-random key or FALSE on failure</p>
</td>
</tr>
<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
</td>
</tr>
</tbody>
</table>
<p>Derives a key from another, presumably weaker key.</p>
<p>This method is used internally to derive an encryption and HMAC key
from your configured <em>encryption_key</em>.</p>
<p>It is publicly available due to its otherwise general purpose. It is
described in <a class="reference external" href="https://tools.ietf.org/rfc/rfc5869.txt">RFC 5869</a>.</p>
<p>However, as opposed to the description in RFC 5869, this implementation
doesn’t support SHA1.</p>
<p>Example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$hmac_key</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">hkdf</span><span class="p">(</span>
        <span class="nv">$key</span><span class="p">,</span>
        <span class="s1">&#39;sha512&#39;</span><span class="p">,</span>
        <span class="k">NULL</span><span class="p">,</span>
        <span class="k">NULL</span><span class="p">,</span>
        <span class="s1">&#39;authentication&#39;</span>
<span class="p">);</span>

<span class="c1">// $hmac_key is a pseudo-random key with a length of 64 bytes</span>
</pre></div>
</div>
</dd></dl>

</dd></dl>

</div>
</div>


          </div>
          <footer>
  
    <div class="rst-footer-buttons" role="navigation" aria-label="footer navigation">
      
        <a href="file_uploading.html" class="btn btn-neutral float-right" title="File Uploading Class">Next <span class="fa fa-arrow-circle-right"></span></a>
      
      
        <a href="encrypt.html" class="btn btn-neutral" title="Encrypt Class"><span class="fa fa-arrow-circle-left"></span> Previous</a>
      
    </div>
  

  <hr/>

  <div role="contentinfo">
    <p>
        &copy; Copyright 2014 - 2018, British Columbia Institute of Technology.
      Last updated on Jan 13, 2018.
    </p>
  </div>

  Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.
  
</footer>
        </div>
      </div>

    </section>

  </div>
  

    <script type="text/javascript">
        var DOCUMENTATION_OPTIONS = {
            URL_ROOT:'../',
            VERSION:'3.1.7',
            COLLAPSE_INDEX:false,
            FILE_SUFFIX:'.html',
            HAS_SOURCE:  false
        };
    </script>
      <script type="text/javascript" src="../_static/jquery.js"></script>
      <script type="text/javascript" src="../_static/underscore.js"></script>
      <script type="text/javascript" src="../_static/doctools.js"></script>

  
    <script type="text/javascript" src="../_static/js/theme.js"></script>
  

  <script type="text/javascript">
      jQuery(function () {
          SphinxRtdTheme.StickyNav.enable();
      });
  </script>
   

</body>
</html>