-
Notifications
You must be signed in to change notification settings - Fork 11
/
encryption.html
3255 lines (3130 loc) · 160 KB
/
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
<!DOCTYPE html>
<html lang="en"><head>
<script src="quarto_files/clipboard/clipboard.min.js"></script>
<script src="quarto_files/quarto-html/tabby.min.js"></script>
<script src="quarto_files/quarto-html/popper.min.js"></script>
<script src="quarto_files/quarto-html/tippy.umd.min.js"></script>
<link href="quarto_files/quarto-html/tippy.css" rel="stylesheet">
<link href="quarto_files/quarto-html/light-border.css" rel="stylesheet">
<link href="quarto_files/quarto-html/quarto-html.min.css" rel="stylesheet" data-mode="light">
<link href="quarto_files/quarto-html/quarto-syntax-highlighting-dark.css" rel="stylesheet" id="quarto-text-highlighting-styles"><meta charset="utf-8">
<meta name="generator" content="quarto-1.5.56">
<title>Encryption</title>
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, minimal-ui">
<link rel="stylesheet" href="quarto_files/revealjs/dist/reset.css">
<link rel="stylesheet" href="quarto_files/revealjs/dist/reveal.css">
<style>
code{white-space: pre-wrap;}
span.smallcaps{font-variant: small-caps;}
div.columns{display: flex; gap: min(4vw, 1.5em);}
div.column{flex: auto; overflow-x: auto;}
div.hanging-indent{margin-left: 1.5em; text-indent: -1.5em;}
ul.task-list{list-style: none;}
ul.task-list li input[type="checkbox"] {
width: 0.8em;
margin: 0 0.8em 0.2em -1em; /* quarto-specific, see https://github.com/quarto-dev/quarto-cli/issues/4556 */
vertical-align: middle;
}
/* CSS for syntax highlighting */
pre > code.sourceCode { white-space: pre; position: relative; }
pre > code.sourceCode > span { line-height: 1.25; }
pre > code.sourceCode > span:empty { height: 1.2em; }
.sourceCode { overflow: visible; }
code.sourceCode > span { color: inherit; text-decoration: inherit; }
div.sourceCode { margin: 1em 0; }
pre.sourceCode { margin: 0; }
@media screen {
div.sourceCode { overflow: auto; }
}
@media print {
pre > code.sourceCode { white-space: pre-wrap; }
pre > code.sourceCode > span { display: inline-block; text-indent: -5em; padding-left: 5em; }
}
pre.numberSource code
{ counter-reset: source-line 0; }
pre.numberSource code > span
{ position: relative; left: -4em; counter-increment: source-line; }
pre.numberSource code > span > a:first-child::before
{ content: counter(source-line);
position: relative; left: -1em; text-align: right; vertical-align: baseline;
border: none; display: inline-block;
-webkit-touch-callout: none; -webkit-user-select: none;
-khtml-user-select: none; -moz-user-select: none;
-ms-user-select: none; user-select: none;
padding: 0 4px; width: 4em;
}
pre.numberSource { margin-left: 3em; padding-left: 4px; }
div.sourceCode
{ color: #f8f8f2; }
@media screen {
pre > code.sourceCode > span > a:first-child::before { text-decoration: underline; }
}
code span { color: #f8f8f2; } /* Normal */
code span.al { color: #f07178; background-color: #2a0f15; font-weight: bold; } /* Alert */
code span.an { color: #d4d0ab; } /* Annotation */
code span.at { color: #00e0e0; } /* Attribute */
code span.bn { color: #d4d0ab; } /* BaseN */
code span.bu { color: #abe338; } /* BuiltIn */
code span.cf { color: #ffa07a; font-weight: bold; } /* ControlFlow */
code span.ch { color: #abe338; } /* Char */
code span.cn { color: #ffd700; } /* Constant */
code span.co { color: #f8f8f2; font-style: italic; } /* Comment */
code span.cv { color: #ffd700; } /* CommentVar */
code span.do { color: #f8f8f2; } /* Documentation */
code span.dt { color: #ffa07a; } /* DataType */
code span.dv { color: #d4d0ab; } /* DecVal */
code span.er { color: #f07178; text-decoration: underline; } /* Error */
code span.ex { color: #00e0e0; font-weight: bold; } /* Extension */
code span.fl { color: #d4d0ab; } /* Float */
code span.fu { color: #ffa07a; } /* Function */
code span.im { color: #abe338; } /* Import */
code span.in { color: #d4d0ab; } /* Information */
code span.kw { color: #ffa07a; font-weight: bold; } /* Keyword */
code span.op { color: #ffa07a; } /* Operator */
code span.ot { color: #00e0e0; } /* Other */
code span.pp { color: #dcc6e0; } /* Preprocessor */
code span.re { color: #00e0e0; background-color: #f8f8f2; } /* RegionMarker */
code span.sc { color: #abe338; } /* SpecialChar */
code span.ss { color: #abe338; } /* SpecialString */
code span.st { color: #abe338; } /* String */
code span.va { color: #00e0e0; } /* Variable */
code span.vs { color: #abe338; } /* VerbatimString */
code span.wa { color: #dcc6e0; } /* Warning */
</style>
<link rel="stylesheet" href="quarto_files/revealjs/dist/theme/quarto.css">
<link rel="stylesheet" href="ics.css">
<link href="quarto_files/revealjs/plugin/quarto-line-highlight/line-highlight.css" rel="stylesheet">
<link href="quarto_files/revealjs/plugin/reveal-menu/menu.css" rel="stylesheet">
<link href="quarto_files/revealjs/plugin/reveal-menu/quarto-menu.css" rel="stylesheet">
<link href="quarto_files/revealjs/plugin/reveal-chalkboard/font-awesome/css/all.css" rel="stylesheet">
<link href="quarto_files/revealjs/plugin/reveal-chalkboard/style.css" rel="stylesheet">
<link href="quarto_files/revealjs/plugin/quarto-support/footer.css" rel="stylesheet">
<style type="text/css">
.callout {
margin-top: 1em;
margin-bottom: 1em;
border-radius: .25rem;
}
.callout.callout-style-simple {
padding: 0em 0.5em;
border-left: solid #acacac .3rem;
border-right: solid 1px silver;
border-top: solid 1px silver;
border-bottom: solid 1px silver;
display: flex;
}
.callout.callout-style-default {
border-left: solid #acacac .3rem;
border-right: solid 1px silver;
border-top: solid 1px silver;
border-bottom: solid 1px silver;
}
.callout .callout-body-container {
flex-grow: 1;
}
.callout.callout-style-simple .callout-body {
font-size: 1rem;
font-weight: 400;
}
.callout.callout-style-default .callout-body {
font-size: 0.9rem;
font-weight: 400;
}
.callout.callout-titled.callout-style-simple .callout-body {
margin-top: 0.2em;
}
.callout:not(.callout-titled) .callout-body {
display: flex;
}
.callout:not(.no-icon).callout-titled.callout-style-simple .callout-content {
padding-left: 1.6em;
}
.callout.callout-titled .callout-header {
padding-top: 0.2em;
margin-bottom: -0.2em;
}
.callout.callout-titled .callout-title p {
margin-top: 0.5em;
margin-bottom: 0.5em;
}
.callout.callout-titled.callout-style-simple .callout-content p {
margin-top: 0;
}
.callout.callout-titled.callout-style-default .callout-content p {
margin-top: 0.7em;
}
.callout.callout-style-simple div.callout-title {
border-bottom: none;
font-size: .9rem;
font-weight: 600;
opacity: 75%;
}
.callout.callout-style-default div.callout-title {
border-bottom: none;
font-weight: 600;
opacity: 85%;
font-size: 0.9rem;
padding-left: 0.5em;
padding-right: 0.5em;
}
.callout.callout-style-default div.callout-content {
padding-left: 0.5em;
padding-right: 0.5em;
}
.callout.callout-style-simple .callout-icon::before {
height: 1rem;
width: 1rem;
display: inline-block;
content: "";
background-repeat: no-repeat;
background-size: 1rem 1rem;
}
.callout.callout-style-default .callout-icon::before {
height: 0.9rem;
width: 0.9rem;
display: inline-block;
content: "";
background-repeat: no-repeat;
background-size: 0.9rem 0.9rem;
}
.callout-title {
display: flex
}
.callout-icon::before {
margin-top: 1rem;
padding-right: .5rem;
}
.callout.no-icon::before {
display: none !important;
}
.callout.callout-titled .callout-body > .callout-content > :last-child {
padding-bottom: 0.5rem;
margin-bottom: 0;
}
.callout.callout-titled .callout-icon::before {
margin-top: .5rem;
padding-right: .5rem;
}
.callout:not(.callout-titled) .callout-icon::before {
margin-top: 1rem;
padding-right: .5rem;
}
/* Callout Types */
div.callout-note {
border-left-color: #4582ec !important;
}
div.callout-note .callout-icon::before {
background-image: url('data:image/png;base64,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');
}
div.callout-note.callout-style-default .callout-title {
background-color: #dae6fb
}
div.callout-important {
border-left-color: #d9534f !important;
}
div.callout-important .callout-icon::before {
background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAAAAXNSR0IArs4c6QAAAERlWElmTU0AKgAAAAgAAYdpAAQAAAABAAAAGgAAAAAAA6ABAAMAAAABAAEAAKACAAQAAAABAAAAIKADAAQAAAABAAAAIAAAAACshmLzAAAEKklEQVRYCcVXTWhcVRS+575MJym48A+hSRFr00ySRQhURRfd2HYjk2SSTokuBCkU2o0LoSKKraKIBTcuFCoidGFD08nkBzdREbpQ1EDNIv8qSGMFUboImMSZd4/f9zJv8ibJMC8xJQfO3HPPPef7zrvvvnvviIkpC9nsw0UttFunbUhpFzFtarSd6WJkStVMw5xyVqYTvkwfzuf/5FgtkVoB0729j1rjXwThS7Vio+Mo6DNnvLfahoZ+i/o32lULuJ3NNiz7q6+pyAUkJaFF6JwaM2lUJlV0MlnQn5aTRbEu0SEqHUa0A4AdiGuB1kFXRfVyg5d87+Dg4DL6m2TLAub60ilj7A1Ec4odSAc8X95sHh7+ZRPCFo6Fnp7HfU/fBng/hi10CjCnWnJjsxvDNxWw0NfV6Rv5GgP3I3jGWXumdTD/3cbEOP2ZbOZp69yniG3FQ9z1jD7bnBu9Fc2tKGC2q+uAJOQHBDRiZX1x36o7fWBs7J9ownbtO+n0/qWkvW7UPIfc37WgT6ZGR++EOJyeQDSb9UB+DZ1G6DdLDzyS+b/kBCYGsYgJbSQHuThGKRcw5xdeQf8YdNHsc6ePXrlSYMBuSIAFTGAtQo+VuALo4BX83N190NWZWbynBjhOHsmNfFWLeL6v+ynsA58zDvvAC8j5PkbOcXCMg2PZFk3q8MjI7WAG/Dp9AwP7jdGBOOQkAvlFUB+irtm16I1Zw9YBcpGTGXYmk3kQIC/Cds55l+iMI3jqhjAuaoe+am2Jw5GT3Nbz3CkE12NavmzN5+erJW7046n/CH1RO/RVa8lBLozXk9uqykkGAyRXLWlLv5jyp4RFsG5vGVzpDLnIjTWgnRy2Rr+tDKvRc7Y8AyZq10jj8DqXdnIRNtFZb+t/ZRtXcDiVnzpqx8mPcDWxgARUqx0W1QB9MeUZiNrV4qP+Ehc+BpNgATsTX8ozYKL2NtFYAHc84fG7ndxUPr+AR/iQSns7uSUufAymwDOb2+NjK27lEFocm/EE2WpyIy/Hi66MWuMKJn8RvxIcj87IM5Vh9663ziW36kR0HNenXuxmfaD8JC7tfKbrhFr7LiZCrMjrzTeGx+PmkosrkNzW94ObzwocJ7A1HokLolY+AvkTiD/q1H0cN48c5EL8Crkttsa/AXQVDmutfyku0E7jShx49XqV3MFK8IryDhYVbj7Sj2P2eBxwcXoe8T8idsKKPRcnZw1b+slFTubwUwhktrfnAt7J++jwQtLZcm3sr9LQrjRzz6cfMv9aLvgmnAGvpoaGLxM4mAEaLV7iAzQ3oU0IvD5x9ix3yF2RAAuYAOO2f7PEFWCXZ4C9Pb2UsgDeVnFSpbFK7/IWu7TPTvBqzbGdCHOJQSxiEjt6IyZmxQyEJHv6xyQsYk//moVFsN2zP6fRImjfq7/n/wFDguUQFNEwugAAAABJRU5ErkJggg==');
}
div.callout-important.callout-style-default .callout-title {
background-color: #f7dddc
}
div.callout-warning {
border-left-color: #f0ad4e !important;
}
div.callout-warning .callout-icon::before {
background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAAAAXNSR0IArs4c6QAAAERlWElmTU0AKgAAAAgAAYdpAAQAAAABAAAAGgAAAAAAA6ABAAMAAAABAAEAAKACAAQAAAABAAAAIKADAAQAAAABAAAAIAAAAACshmLzAAAETklEQVRYCeVWW2gcVRg+58yaTUnizqbipZeX4uWhBEniBaoUX1Ioze52t7sRq6APio9V9MEaoWlVsFasRq0gltaAPuxms8lu0gcviE/FFOstVbSIxgcv6SU7EZqmdc7v9+9mJtNks51NTUH84ed889/PP+cmxP+d5FIbMJmNbpREu4WUkiTtCicKny0l1pIKmBzovF2S+hIJHX8iEu3hZJ5lNZGqyRrGSIQpq15AzF28jgpeY6yk6GVdrfFqdrD6Iw+QlB8g0YS2g7dyQmXM/IDhBhT0UCiRf59lfqmmDvzRt6kByV/m4JjtzuaujMUM2c5Z2d6JdKrRb3K2q6mA+oYVz8JnDdKPmmNthzkAk/lN63sYPgevrguc72aZX/L9C6x09GYyxBgCX4NlvyGUHOKELlm5rXeR1kchuChJt4SSwyddZRXgvwMGvYo4QSlk3/zkHD8UHxwVJA6zjZZqP8v8kK8OWLnIZtLyCAJagYC4rTGW/9Pqj92N/c+LUaAj27movwbi19tk/whRCIE7Q9vyI6yvRpftAKVTdUjOW40X3h5OXsKCdmFcx0xlLJoSuQngnrJe7Kcjm4OMq9FlC7CMmScQANuNvjfP3PjGXDBaUQmbp296S5L4DrpbrHN1T87ZVEZVCzg1FF0Ft+dKrlLukI+/c9ENo+TvlTDbYFvuKPtQ9+l052rXrgKoWkDAFnvh0wTOmYn8R5f4k/jN/fZiCM1tQx9jQQ4ANhqG4hiL0qIFTGViG9DKB7GYzgubnpofgYRwO+DFjh0Zin2m4b/97EDkXkc+f6xYAPX0KK2I/7fUQuwzuwo/L3AkcjugPNixC8cHf0FyPjWlItmLxWw4Ou9YsQCr5fijMGoD/zpdRy95HRysyXA74MWOnscpO4j2y3HAVisw85hX5+AFBRSHt4ShfLFkIMXTqyKFc46xdzQM6XbAi702a7sy04J0+feReMFKp5q9esYLCqAZYw/k14E/xcLLsFElaornTuJB0svMuJINy8xkIYuL+xPAlWRceH6+HX7THJ0djLUom46zREu7tTkxwmf/FdOZ/sh6Q8qvEAiHpm4PJ4a/doJe0gH1t+aHRgCzOvBvJedEK5OFE5jpm4AGP2a8Dxe3gGJ/pAutug9Gp6he92CsSsWBaEcxGx0FHytmIpuqGkOpldqNYQK8cSoXvd+xLxXADw0kf6UkJNFtdo5MOgaLjiQOQHcn+A6h5NuL2s0qsC2LOM75PcF3yr5STuBSAcGG+meA14K/CI21HcS4LBT6tv0QAh8Dr5l93AhZzG5ZJ4VxAqdZUEl9z7WJ4aN+svMvwHHL21UKTd1mqvChH7/Za5xzXBBKrUcB0TQ+Ulgkfbi/H/YT5EptrGzsEK7tR1B7ln9BBwckYfMiuSqklSznIuoIIOM42MQO+QnduCoFCI0bpkzjCjddHPN/F+2Yu+sd9bKNpVwHhbS3LluK/0zgfwD0xYI5dXuzlQAAAABJRU5ErkJggg==');
}
div.callout-warning.callout-style-default .callout-title {
background-color: #fcefdc
}
div.callout-tip {
border-left-color: #02b875 !important;
}
div.callout-tip .callout-icon::before {
background-image: url('data:image/png;base64,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');
}
div.callout-tip.callout-style-default .callout-title {
background-color: #ccf1e3
}
div.callout-caution {
border-left-color: #fd7e14 !important;
}
div.callout-caution .callout-icon::before {
background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAAAAXNSR0IArs4c6QAAAERlWElmTU0AKgAAAAgAAYdpAAQAAAABAAAAGgAAAAAAA6ABAAMAAAABAAEAAKACAAQAAAABAAAAIKADAAQAAAABAAAAIAAAAACshmLzAAACV0lEQVRYCdVWzWoUQRCuqp2ICBLJXgITZL1EfQDBW/bkzUMUD7klD+ATSHBEfAIfQO+iXsWDxJsHL96EHAwhgzlkg8nBg25XWb0zIb0zs9muYYWkoKeru+vn664fBqElyZNuyh167NXJ8Ut8McjbmEraKHkd7uAnAFku+VWdb3reSmRV8PKSLfZ0Gjn3a6Xlcq9YGb6tADjn+lUfTXtVmaZ1KwBIvFI11rRXlWlatwIAAv2asaa9mlB9wwygiDX26qaw1yYPzFXg2N1GgG0FMF8Oj+VIx7E/03lHx8UhvYyNZLN7BwSPgekXXLribw7w5/c8EF+DBK5idvDVYtEEwMeYefjjLAdEyQ3M9nfOkgnPTEkYU+sxMq0BxNR6jExrAI31H1rzvLEfRIdgcv1XEdj6QTQAS2wtstEALLG1yEZ3QhH6oDX7ExBSFEkFINXH98NTrme5IOaaA7kIfiu2L8A3qhH9zRbukdCqdsA98TdElyeMe5BI8Rs2xHRIsoTSSVFfCFCWGPn9XHb4cdobRIWABNf0add9jakDjQJpJ1bTXOJXnnRXHRf+dNL1ZV1MBRCXhMbaHqGI1JkKIL7+i8uffuP6wVQAzO7+qVEbF6NbS0LJureYcWXUUhH66nLR5rYmva+2tjRFtojkM2aD76HEGAD3tPtKM309FJg5j/K682ywcWJ3PASCcycH/22u+Bh7Aa0ehM2Fu4z0SAE81HF9RkB21c5bEn4Dzw+/qNOyXr3DCTQDMBOdhi4nAgiFDGCinIa2owCEChUwD8qzd03PG+qdW/4fDzjUMcE1ZpIAAAAASUVORK5CYII=');
}
div.callout-caution.callout-style-default .callout-title {
background-color: #ffe5d0
}
</style>
<style type="text/css">
.reveal div.sourceCode {
margin: 0;
overflow: auto;
}
.reveal div.hanging-indent {
margin-left: 1em;
text-indent: -1em;
}
.reveal .slide:not(.center) {
height: 100%;
}
.reveal .slide.scrollable {
overflow-y: auto;
}
.reveal .footnotes {
height: 100%;
overflow-y: auto;
}
.reveal .slide .absolute {
position: absolute;
display: block;
}
.reveal .footnotes ol {
counter-reset: ol;
list-style-type: none;
margin-left: 0;
}
.reveal .footnotes ol li:before {
counter-increment: ol;
content: counter(ol) ". ";
}
.reveal .footnotes ol li > p:first-child {
display: inline-block;
}
.reveal .slide ul,
.reveal .slide ol {
margin-bottom: 0.5em;
}
.reveal .slide ul li,
.reveal .slide ol li {
margin-top: 0.4em;
margin-bottom: 0.2em;
}
.reveal .slide ul[role="tablist"] li {
margin-bottom: 0;
}
.reveal .slide ul li > *:first-child,
.reveal .slide ol li > *:first-child {
margin-block-start: 0;
}
.reveal .slide ul li > *:last-child,
.reveal .slide ol li > *:last-child {
margin-block-end: 0;
}
.reveal .slide .columns:nth-child(3) {
margin-block-start: 0.8em;
}
.reveal blockquote {
box-shadow: none;
}
.reveal .tippy-content>* {
margin-top: 0.2em;
margin-bottom: 0.7em;
}
.reveal .tippy-content>*:last-child {
margin-bottom: 0.2em;
}
.reveal .slide > img.stretch.quarto-figure-center,
.reveal .slide > img.r-stretch.quarto-figure-center {
display: block;
margin-left: auto;
margin-right: auto;
}
.reveal .slide > img.stretch.quarto-figure-left,
.reveal .slide > img.r-stretch.quarto-figure-left {
display: block;
margin-left: 0;
margin-right: auto;
}
.reveal .slide > img.stretch.quarto-figure-right,
.reveal .slide > img.r-stretch.quarto-figure-right {
display: block;
margin-left: auto;
margin-right: 0;
}
</style>
</head>
<body class="quarto-dark">
<div class="reveal">
<div class="slides">
<section id="title-slide" class="quarto-title-block center">
<h1 class="title">CS 3710</h1>
<h2 class="subtitle">Introduction to Cybersecurity</h2>
<p class="titlep"> </p>
<div class="titlesmall"><p>
<a href="http://www.cs.virginia.edu/~asb">Aaron Bloomfield</a> ([email protected])<br>
<a href="http://github.com/aaronbloomfield/ccc">@github</a> | <a href="index.html">↑</a> | <a href="?print-pdf"><img class="print" width="20" src="../slides/images/print-icon.svg" style="top:0px;vertical-align:middle;background-color:transparent"></a>
</p></div>
<p class="titlep"> </p>
<h2 class="subtitle">Encryption</h2>
</section><section id="TOC">
<nav role="doc-toc">
<h2 id="toc-title">Contents</h2>
<ul>
<li><a href="#/introduction" id="/toc-introduction">Introduction</a></li>
<li><a href="#/classical-ciphers-and-rotor-machines" id="/toc-classical-ciphers-and-rotor-machines">Classical ciphers and rotor machines</a></li>
<li><a href="#/private-key-symmetric-ciphers" id="/toc-private-key-symmetric-ciphers">Private key “symmetric” ciphers</a></li>
<li><a href="#/number-theory" id="/toc-number-theory">Number Theory</a></li>
<li><a href="#/rsa" id="/toc-rsa">RSA</a></li>
<li><a href="#/randomness" id="/toc-randomness">Randomness</a></li>
<li><a href="#/hashing" id="/toc-hashing">Hashing</a></li>
<li><a href="#/applied-cryptography" id="/toc-applied-cryptography">Applied Cryptography</a></li>
<li><a href="#/top-10-uncracked-codes" id="/toc-top-10-uncracked-codes">Top 10 uncracked codes</a></li>
</ul>
</nav>
</section>
<section>
<section id="introduction" class="title-slide slide level1 center">
<h1>Introduction</h1>
</section>
<section id="telnet-and-tcpdump" class="slide level2">
<h2>Telnet and tcpdump</h2>
<ul>
<li>Telnet is the old version of ssh (aka SecureCRT), and sends all data as plaintext</li>
<li>tcpdump will dump all data sent over a TCP/IP interface</li>
<li>The next slide shows a tcpdump
<ul>
<li>… but without the data in the packets, which has been eliminated from this slide</li>
</ul></li>
<li>It’s easy to show that data, though</li>
</ul>
</section>
<section class="slide level2">
<img data-src="images/encryption/tcpdump.png" class="r-stretch"></section>
<section id="codes-versus-ciphers" class="slide level2">
<h2>Codes versus Ciphers</h2>
<ul>
<li>Codes change the meaning of words, ciphers encrypt them</li>
<li>Coded messages:
<ul>
<li>“The light is on in the attic”</li>
</ul></li>
<li>Cipher’ed messages:
<ul>
<li>wkh txlfn eurzq ira mxpsv ryhu wkh odcb grj</li>
<li>wecrl teerd soeef eaoca ivden</li>
</ul></li>
<li><a href="http://en.wikipedia.org/wiki/Cipher#Ciphers_versus_codes">Reference</a></li>
</ul>
</section>
<section id="codes" class="slide level2">
<h2>Codes</h2>
<ul>
<li>One- and two-part codes: contains one or two books that correlate coded words with their plaintext meanings</li>
<li>One-time code: a pre-arranged word or phrase intended to be used only once, and to convey a message
<ul>
<li>“Over all of Spain, the sky is clear” - over the radio, it started the Spanish revolt of 1936</li>
</ul></li>
</ul>
</section>
<section id="codes-1" class="slide level2">
<h2>Codes</h2>
<ul>
<li>Idiot code: any sentence with ‘day’ and ‘night’ means ‘attack’ the location in the sentence
<ul>
<li>Plaintext: Attack Gotham.</li>
<li>Codetext: We walked day and night through the streets but couldn’t find it! Tomorrow we’ll head into Gotham.</li>
</ul></li>
<li><a href="http://en.wikipedia.org/wiki/Code_%28cryptography%29">Reference</a></li>
</ul>
</section>
<section id="security-through-obscurity" class="slide level2">
<h2>Security through obscurity</h2>
<ul>
<li>The use of secrecy to hide the cryptographic system being used
<ul>
<li>Contrast this with algorithms such as RSA, which are publically analyzed</li>
</ul></li>
<li>The problems is that somebody will figure out how it works (“many eyes make all bugs shallow” - Linus Torvalds)
<ul>
<li>And then, if there is a flaw (due to lack of peer review), the system is vulnerable</li>
</ul></li>
<li><a href="http://en.wikipedia.org/wiki/Security_by_obscurity">Reference</a></li>
</ul>
</section>
<section id="block-ciphers-vs.-stream-ciphers" class="slide level2">
<h2>Block-ciphers vs. stream ciphers</h2>
<ul>
<li>Block ciphers require a block of text (perhaps 1 Kb, for example)
<ul>
<li><a href="http://en.wikipedia.org/wiki/Block_cipher">Reference</a></li>
</ul></li>
<li>Stream ciphers encrypt data as it is provided, character-by-character
<ul>
<li>I prefer the name ‘character cipher’ over ‘stream cipher’</li>
<li><a href="http://en.wikipedia.org/wiki/Stream_cipher">Reference</a></li>
</ul></li>
</ul>
</section>
<section id="cipher-taxonomy" class="slide level2">
<h2>Cipher Taxonomy</h2>
<p><img data-src="images/encryption/cipher-taxonomy.png" alt="cipher taxonomy"> - <a href="http://en.wikipedia.org/wiki/Ciphers">Reference</a></p>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
</section></section>
<section>
<section id="classical-ciphers-and-rotor-machines" class="title-slide slide level1 center">
<h1>Classical ciphers and rotor machines</h1>
</section>
<section id="caesar-cipher" class="slide level2">
<h2>Caesar Cipher</h2>
<ul>
<li>Julius Caesar used it to send military messages
<ul>
<li>Rome’s enemies were unable to crack it!</li>
</ul></li>
<li>A simple substitution cipher
<ul>
<li>Encryption: replace any letter with the letter 3 spots beyond</li>
</ul></li>
<li>Decryption: the same, but go 3 letters back</li>
</ul>
</section>
<section id="caesar-cipher-1" class="slide level2">
<h2>Caesar Cipher</h2>
<img data-src="images/encryption/caesar-cipher.png" class="r-stretch"></section>
<section id="caesar-cipher-analysis" class="slide level2">
<h2>Caesar Cipher analysis</h2>
<ul>
<li>Example:
<ul>
<li>Plaintext: the quick brown fox jumps over the lazy dog</li>
<li>Ciphertext: WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ</li>
</ul></li>
<li>Pros:
<ul>
<li>Easy to encrypt and decrypt by hand</li>
</ul></li>
<li>Cons:
<ul>
<li>Easy to crack by hand</li>
</ul></li>
</ul>
</section>
<section id="caesar-cipher-analysis-1" class="slide level2">
<h2>Caesar Cipher analysis</h2>
<ul>
<li>Cracking
<ul>
<li>There are only 26 possibilities!
<ul>
<li>Well, 25 really – nobody would encrypt with a key of 0 or 26…</li>
</ul></li>
<li>A program could do this in a matter of microseconds; a person in a matter of minutes</li>
<li>Example: crack “s psxn iyeb vkmu yp pksdr nscdeblsxq” online <a href="http://md5decrypt.net/en/Caesar/">here</a> (select ‘bruteforce’)</li>
</ul></li>
<li>Substitution ciphers can be more complex
<ul>
<li>Having a mapping, rather than a rotation</li>
</ul></li>
</ul>
</section>
<section id="cracking-a-substitution-cipher" class="slide level2">
<h2>Cracking a substitution cipher</h2>
<ul>
<li>Cracking a Caesar cipher is trivial
<ul>
<li>There are only 26 possibilities</li>
</ul></li>
<li>But what about a more general substitution cipher?</li>
<li>Letter frequency analysis
<ul>
<li>‘e’ is the most common letter (12.7%)</li>
<li>‘z’ is the least common letter (0.1%)</li>
<li><a href="http://en.wikipedia.org/wiki/Letter_frequencies">Reference</a></li>
</ul></li>
<li>Still very easy to crack</li>
</ul>
</section>
<section id="vigenere-cipher" class="slide level2">
<h2>Vigenere cipher</h2>
<ul>
<li>If a Caesar Cipher is a alphabetic substitution, then a Vigenere cipher is a poly-alphabetic substitution cipher</li>
<li>The table used is the shown on the next slide</li>
<li>Suppose the message to encrypt is “attackatdawn”</li>
<li>And the keyword is “lemon”</li>
</ul>
</section>
<section id="vigenere-cipher-table" class="slide level2">
<h2>Vigenere cipher table</h2>
<img data-src="images/encryption/vigenere-cipher.png" class="r-stretch"></section>
<section id="vigenere-cipher-1" class="slide level2">
<h2>Vigenere cipher</h2>
<ul>
<li>Cipher algorithm:
<ul>
<li>Repeat the keyword until it matches the length of the message
<ul>
<li>“attackatdawn” is 12 letters; the new keyword is “lemonlemonle”</li>
</ul></li>
<li>Encrypt the first letter of the message using the first letter of the keyword, etc.
<ul>
<li>‘a’ is encrypted with ‘l’, ‘t’ with ‘e’, etc.</li>
</ul></li>
<li>The encryption is done by finding the row of the message character, and the column of the keyword</li>
</ul></li>
</ul>
</section>
<section id="vigenere-cipher-2" class="slide level2">
<h2>Vigenere cipher</h2>
<p><img data-src="images/encryption/vigenere-cipher.png" alt="vigenere table"> Encrypt “attackatdawn” with “lemon”</p>
</section>
<section id="vigenere-cipher-result" class="slide level2">
<h2>Vigenere cipher result</h2>
<ul>
<li>Plaintext: ATTACKATDAWN</li>
<li>Key: LEMONLEMONLE</li>
<li>Ciphertext: LXFOPVEFRNHR</li>
</ul>
</section>
<section id="vigenere-cipher-analysis" class="slide level2">
<h2>Vigenere cipher analysis</h2>
<ul>
<li>It’s stronger than a Caesar Cipher
<ul>
<li>‘e’ can be encrypted multiple ways</li>
</ul></li>
<li>The weakness is the repeating key
<ul>
<li>If you guess the length of the key (or try all possible lengths), then you can crack it</li>
<li>Let’s say the key is length 5 (a guess, perhaps)</li>
<li>Then you simply do 5 interwoven Caesar Cipher cracks</li>
</ul></li>
<li>What if the key is as long as the message?</li>
<li><a href="http://en.wikipedia.org/wiki/Vigenere_cipher">Reference</a></li>
</ul>
</section>
<section id="one-time-pad-otp" class="slide level2">
<h2>One-time pad (OTP)</h2>
<ul>
<li>A substitution cipher</li>
<li>Take a <em>random</em> string that is as long as the plain text you want encrypt
<ul>
<li>Use modular arithmetic (or XOR, or Vigenere) to determine the encrypted version</li>
<li>Plain text: helloworld</li>
<li>One-time pad: zdxwhtsvtv</li>
<li>Encrypted: hijiwqhnfz</li>
</ul></li>
<li><a href="http://en.wikipedia.org/wiki/One-time_pad">Reference</a></li>
</ul>
</section>
<section id="one-time-pad-otp-analysis" class="slide level2">
<h2>One-time pad (OTP) analysis</h2>
<ul>
<li>Pros
<ul>
<li>Proven to be perfectly secure if:
<ul>
<li>the pad is truly random</li>
<li>the pad is only used once</li>
<li>the pad is kept secret</li>
</ul></li>
<li>This, it is the ONLY cryptosystem with perfect secrecy</li>
<li>It can be performed by hand</li>
</ul></li>
</ul>
</section>
<section id="one-time-pad-otp-analysis-1" class="slide level2">
<h2>One-time pad (OTP) analysis</h2>
<ul>
<li>Cons:
<ul>
<li>Good for short messages; it’s hard to transport large pads (i.e. network communication)</li>
<li>Does not provide message authentication</li>
<li>How do you get the pad to the recipient?</li>
</ul></li>
</ul>
</section>
<section id="re-using-a-one-time-pad" class="slide level2">
<h2>Re-using a one-time pad</h2>
<table class="transparent">
<tbody><tr>
<td>
Use an OTP:
</td>
<td>
<img alt="re-using OTP" style="vertical-align:middle;display:initial" src="images/encryption/otp-1.png"> ⊕ <img alt="re-using OTP" style="vertical-align:middle;display:initial" src="images/encryption/otp.png"> = <img alt="re-using OTP" style="vertical-align:middle;display:initial;border:2px solid red" src="images/encryption/otp-1e.png">
</td>
</tr>
<tr class="fragment">
<td>
Re-use the<br>same OTP:
</td>
<td>
<img alt="re-using OTP" style="vertical-align:middle;display:initial" src="images/encryption/otp-2.png"> ⊕ <img alt="re-using OTP" style="vertical-align:middle;display:initial" src="images/encryption/otp.png"> = <img alt="re-using OTP" style="vertical-align:middle;display:initial;border:2px solid blue" src="images/encryption/otp-2e.png">
</td>
</tr>
<tr class="fragment">
<td>
Extract<br>the images:
</td>
<td>
<img alt="re-using OTP" style="vertical-align:middle;display:initial;border:2px solid red" src="images/encryption/otp-1e.png"> ⊕ <img alt="re-using OTP" style="vertical-align:middle;display:initial;border:2px solid blue" src="images/encryption/otp-2e.png"> = <img alt="re-using OTP" style="vertical-align:middle;display:initial" src="images/encryption/otp-ans.png">
</td>
</tr>
</tbody></table>
<p>
This example from <a href="https://crypto.stackexchange.com/questions/59/taking-advantage-of-one-time-pad-key-reuse">StackExchange</a>
</p>
</section>
<section id="route-cipher" class="slide level2">
<h2>Route cipher</h2>
<ul>
<li>A transposition cipher
<ul>
<li>The plain text is written in a grid</li>
<li>The secret is the direction to read the cipher text</li>
</ul></li>
<li>Plain text: ‘we are discovered flee at once’</li>
<li>Cipher progression:</li>
</ul>
<div class="sourceCode" id="cb1"><pre class="sourceCode numberSource text number-lines code-with-copy"><code class="sourceCode"><span id="cb1-1"><a href=""></a>R E D F L E E A W </span>
<span id="cb1-2"><a href=""></a>E J X E C N O T E </span>
<span id="cb1-3"><a href=""></a>V O C S I D E R A </span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<ul>
<li>Key: “spiral inwards, clockwise, starting from the top right”</li>
<li>Cipher text: REDFLEEAWEJXECNOTEVOCSIDERA</li>
<li><a href="http://en.wikipedia.org/wiki/Transposition_cipher">Reference</a></li>
</ul>
</section>
<section id="rail-fence-cipher" class="slide level2">
<h2>Rail fence cipher</h2>
<ul>
<li>A transposition cipher
<ul>
<li>The plain text is written up and down on successive ‘rails’ of a fence</li>
<li>The encrypted text is then read off in rows</li>
</ul></li>
<li>Plain text: ‘we are discovered flee at once’</li>
<li>Cipher progression:</li>
</ul>
<div class="sourceCode" id="cb2"><pre class="sourceCode numberSource text number-lines code-with-copy"><code class="sourceCode"><span id="cb2-1"><a href=""></a>W . . . E . . . C . . . R . . . L . . . T . . . E</span>
<span id="cb2-2"><a href=""></a>. E . R . D . S . O . E . E . F . E . A . O . C .</span>
<span id="cb2-3"><a href=""></a>. . A . . . I . . . V . . . D . . . E . . . N . .</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<ul>
<li>Cipher text: WECRL TEERD SOEEF EAOCA IVDEN</li>
<li><a href="http://en.wikipedia.org/wiki/Transposition_cipher">Reference</a></li>
</ul>
</section>
<section id="ww2-navajo-code-talkers" class="slide level2">
<h2>WW2 Navajo Code Talkers</h2>
<ul>
<li>Used during the American strategy of island-hopping in the Pacific during WW2</li>
<li>Native Navajo speakers (which were only in the US!) were used to send messages back and forth over radio frequencies that could be spied on</li>
<li>The ‘encryption’ or cipher was the language
<ul>
<li>There were no written documents or dictionaries in existence</li>
<li>Other than Navajo Native Americans (all in the US, obviously), there were only 30 or so people who were fluent</li>
</ul></li>
</ul>
</section>
<section id="ww2-navajo-code-talkers-1" class="slide level2">
<h2>WW2 Navajo Code Talkers</h2>
<ul>
<li>But there was a code as well
<ul>
<li>Navajo words were translated into their English equivalents</li>
<li>The first letter of each English translated word was combined to form the message</li>
<li>If you didn’t know this, it would be a series of unconnected Navajo words</li>
</ul></li>
<li>It has been stated that the US would not have won the Battle of Iwo Jima without the Navajo code talkers</li>
<li>References <a href="http://en.wikipedia.org/wiki/Code_talker#Use_of_Navajo%29">1</a> and <a href="http://www.bingaman.senate.gov/features/codetalkers/">2</a></li>
</ul>
</section>
<section id="rotor-machines" class="slide level2">
<h2>Rotor machines</h2>
<ul>
<li>It performs a simple substitution of letters</li>
<li>After encrypting each letter, the rotors advance positions</li>
<li>Thus, they implement a poly-alphabetic substitution cipher
<ul>
<li>Similar to the Vigenere cipher</li>
</ul></li>
<li><a href="http://en.wikipedia.org/wiki/Rotor_machine">Reference</a></li>
</ul>
</section>
<section id="rotor-machines-1" class="slide level2">
<h2>Rotor machines</h2>
<img data-src="images/encryption/rotor-machine.png" class="r-stretch"></section>
<section id="enigma-machine" class="slide level2">
<h2>Enigma machine</h2>
<ul>
<li>Most famous rotor machine</li>
<li>Used by many governments in WW2, especially Nazi Germany</li>
<li>The Allies were able to decrypt Nazi messages
<ul>
<li>But not through crypto-graphically cracking the code!</li>
</ul></li>
<li>This is estimated to have shortened the war in the European theater by 2 years</li>
<li><a href="http://en.wikipedia.org/wiki/Enigma_machine">Reference</a></li>
</ul>
<!-- .slide: class="no-border" -->
</section>
<section id="enigma-machine-1" class="slide level2">
<h2>Enigma machine</h2>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<img data-src="images/encryption/enigma-machine.png" class="r-stretch"></section></section>
<section>
<section id="private-key-symmetric-ciphers" class="title-slide slide level1 center">
<h1>Private key “symmetric” ciphers</h1>
</section>
<section id="data-encryption-standard-des" class="slide level2">
<h2>Data Encryption Standard (<a href="http://en.wikipedia.org/wiki/Data_Encryption_Standard">DES</a>)</h2>
<ul>
<li>Adopted in 1976, it’s a private-key encryption/decryption block cipher</li>
<li>Briefly, it does a lot of (invertible) bit-shifting in rounds to encrypt/decrypt a message</li>
<li>How to crack?
<ul>
<li>It is susceptible to brute force attacks (<span class="math inline">\(2^{56} = 7 * 10^{16}\)</span> keys)</li>
</ul></li>
<li>Solution: use DES three times => “Triple DES”
<ul>
<li>Use a 56*3 = 168 bit key, and encrypt the message three times, once with each key</li>
</ul></li>
</ul>
</section>
<section id="cracking-triple-des-encryption" class="slide level2">
<h2>Cracking Triple DES encryption</h2>
<ul>
<li>Brute-force attacks:
<ul>
<li><span class="math inline">\(2^{168}\)</span> keys, but due to various mathematical properties, this ends up being <span class="math inline">\(2^{112}\)</span> different keys</li>
</ul></li>
<li>“The best attack known on 3-key TDES requires around <span class="math inline">\(2^{32}\)</span> known plaintexts, <span class="math inline">\(2^{113}\)</span> steps, <span class="math inline">\(2^{90}\)</span> single DES encryptions, and <span class="math inline">\(2^{88}\)</span> memory”</li>
<li>NIST (National Institute of Standards and Technology) considers it secure through 2030</li>
</ul>
</section>
<section id="des-conspiracy-theories" class="slide level2">
<h2>DES conspiracy theories</h2>
<ul>
<li>NSA was involved with DES’ creation
<ul>
<li>They convinced IBM to lower the key length from 128 to 64, and then to 56</li>
<li>And kept many of the details secret</li>
<li>Many well-respected people criticized the NSA for “improper interference” with the algorithm</li>
</ul></li>
<li>In 1977, Diffie and Hellman (major names in cryptography) proposed a $20 million machine that could crack a DES message in a single day</li>
<li>It’s known that the NSA had the budget for such a machine. But did they build it?</li>
</ul>
</section>
<section id="advanced-encryption-standard-aes" class="slide level2">
<h2>Advanced Encryption Standard (AES)</h2>
<ul>
<li>The successor to DES</li>
<li>Has three possible key lengths: 128, 192, and 256</li>
<li>NSA approved this standard, and kept the process open</li>
<li>Like DES, it’s a series of (invertible) bit-shifting in rounds to encrypt/decrypt a message</li>
<li>Many worry about the security of the standard
<ul>
<li>… that somebody may figure a way to crack it mathematically, in particular</li>
</ul></li>
<li><a href="http://en.wikipedia.org/wiki/Advanced_Encryption_Standard">Reference</a></li>
</ul>
</section>
<section id="aes-overview" class="slide level2">
<h2>AES Overview</h2>
<ol type="1">
<li>Determine number of rounds, <span class="math inline">\(r\)</span>:
<ul>
<li>10, 12, or 14 rounds for 128-bit, 192-bit, and 256-bit keys</li>
</ul></li>
<li>KeyExpansion: derive round keys from Key Round Schedule</li>
<li>Round 1: AddRoundKey: XOR with round key</li>
<li>Rounds 2 through <span class="math inline">\(r-1\)</span>:
<ul>
<li>SubBytes, ShiftRows, MixColumns, AddRoundKey</li>
</ul></li>
<li>Final round <span class="math inline">\(r\)</span>:
<ul>
<li>SubBytes, ShiftRows, AddRoundKey</li>
</ul></li>
</ol>
</section>
<section id="key-round-schedule" class="slide level2">
<h2>Key Round Schedule</h2>
<p><a href="https://commons.wikimedia.org/wiki/File:AES-Key_Schedule_128-bit_key.svg"><img data-src="https://upload.wikimedia.org/wikipedia/commons/b/be/AES-Key_Schedule_128-bit_key.svg" style="width:500px;float:right;margin:10px;border:10px solid white"></a></p>
<ul>
<li>Let:
<ul>
<li><span class="math inline">\(N\)</span>: key length in 32-bit words (4, 6, or 8)</li>
<li><span class="math inline">\(K_0, K_1, \ldots K_{N-1}\)</span>: 32-bit words of the key</li>
<li><code>RotWord</code> is a left rotation by 1</li>
<li><code>SubWord</code> is a lookup</li>
<li><span class="math inline">\(R_{con}\)</span> is a fixed round constant</li>
</ul></li>
<li>Then repeat the image many times</li>
<li>It’s fixed for that one key, so only has to be computed once</li>
</ul>
</section>
<section id="aes-subbytes-step" class="slide level2">
<h2>AES: SubBytes step</h2>
<p><a href="https://commons.wikimedia.org/wiki/File:AES-SubBytes.svg"><img src="https://upload.wikimedia.org/wikipedia/commons/a/a4/AES-SubBytes.svg" style="width:70%"></a></p>
<ul>
<li>Input is mapped to its mult. inverse in a finite field</li>
<li>Bytes are replaced based on a fixed substitution table
<ul>
<li>Fixed for all of AES</li>
</ul></li>
<li>Called the <a href="https://en.wikipedia.org/wiki/Rijndael_S-box">Rijndael S-box</a></li>
</ul>
</section>
<section id="aes-shiftrows-step" class="slide level2">
<h2>AES: ShiftRows step</h2>
<p><a href="https://commons.wikimedia.org/wiki/File:AES-ShiftRows.svg"><img data-src="https://upload.wikimedia.org/wikipedia/commons/6/66/AES-ShiftRows.svg"></a></p>
<ul>
<li>Rows are shifted cyclically to the left</li>
<li>This provides <em>diffusion</em></li>
</ul>
<!-- .slide: class="right-float-img-600" -->
</section>
<section id="aes-mixcolumns-step" class="slide level2">
<h2>AES: MixColumns step</h2>
<p><a href="https://commons.wikimedia.org/wiki/File:AES-MixColumns.svg"><img data-src="https://upload.wikimedia.org/wikipedia/commons/7/76/AES-MixColumns.svg"></a></p>
<ul>
<li>The values are transformed according to the following matrix operation</li>
<li>This also provides <em>diffusion</em></li>
</ul>
<br clear="all">
<div style="font-size:0.75em">
<p><span class="math inline">\(\begin{bmatrix} b_{0,j} \\\ b_{1,j} \\\ b_{2,j} \\\ b_{3,j} \end{bmatrix} =
\begin{bmatrix} 2&3&1&1 \\\ 1&2&3&1 \\\ 1&1&2&3 \\\ 3&1&1&2 \end{bmatrix}
\begin{bmatrix} a_{0,j} \\\ a_{1,j} \\\ a_{2,j} \\\ a_{3,j} \end{bmatrix}
\text{ for }0 \le j \le 3\)</span></p>
</div>
<!-- .slide: class="right-float-img-800" -->
</section>
<section id="aes-addroundkey-step" class="slide level2">
<h2>AES: AddRoundKey step</h2>
<p><a href="https://commons.wikimedia.org/wiki/File:AES-AddRoundKey.svg"><img data-src="https://upload.wikimedia.org/wikipedia/commons/a/ad/AES-AddRoundKey.svg" style="width:600px;float:right;margin:10px;border:10px solid white"></a></p>
<ul>
<li>Derive a subkey from the main key via the AES key schedule</li>
<li>Subkey is then XOR’ed with the state</li>
</ul>
</section>
<section id="aes-overview-1" class="slide level2">
<h2>AES Overview</h2>
<ol type="1">
<li>Determine number of rounds, <span class="math inline">\(r\)</span>:
<ul>
<li>10, 12, or 14 rounds for 128-bit, 192-bit, and 256-bit keys</li>
</ul></li>
<li>KeyExpansion: derive round keys from the AES Key Round Schedule</li>
<li>Round 1: AddRoundKey: XOR with round key</li>
<li>Rounds 2 through <span class="math inline">\(r-1\)</span>:
<ul>
<li>SubBytes, ShiftRows, MixColumns, AddRoundKey</li>
</ul></li>
<li>Final round <span class="math inline">\(r\)</span>:
<ul>
<li>SubBytes, ShiftRows, AddRoundKey</li>
</ul></li>
</ol>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
</section></section>
<section>
<section id="number-theory" class="title-slide slide level1 center">
<h1>Number Theory</h1>
</section>
<section id="is-that-number-prime" class="slide level2">
<h2>Is that number prime?</h2>
<ul>
<li>Use the Fermat primality test</li>
<li>Given:</li>
<li><span class="math inline">\(n\)</span>: the number to test for primality</li>
<li><span class="math inline">\(k\)</span>: the number of times to test (the certainty)</li>
<li>The algorithm is:</li>
</ul>
<div class="sourceCode" id="cb3"><pre class="sourceCode numberSource text number-lines code-with-copy"><code class="sourceCode"><span id="cb3-1"><a href=""></a>repeat k times: </span>
<span id="cb3-2"><a href=""></a> pick a random number in the range [1, n-1]</span>
<span id="cb3-3"><a href=""></a> if a^{n-1} mod n != 1 then return composite</span>
<span id="cb3-4"><a href=""></a>return probably prime</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
</section>
<section id="is-that-number-prime-1" class="slide level2">
<h2>Is that number prime?</h2>
<ul>
<li>The algorithm is:</li>
</ul>