The secrets of cryptography

Alice and Bob have secrets they want to talk about without Eve being able to listen in. Worse yet, the mischievous Mallory delights in changing messages sent between parties. In such a hostile environment how can Alice talk to Bob without their messages being overheard and how can she be sure that it was Bob that sent the message in the first place?

This talk will take a brief look at historic codes and ciphers before taking a look at modern day Cryptography. If you want to be able to know the difference between a block cipher and a stream cipher or get a glimpse into the mathematics behind public key Cryptography this talk is for you.

Cipher challenge here: http://tiny.cc/0qq6by

Transcript

1. The Secrets of Cryptography Christopher Riley PHP South Coast, 2016 1
2. Introduction
3. Cryptography is HARD 2
4. Historic ciphers
5. The ceasar shift
6. The ceasar shift 3
7. The substitution cipher
8. The substitution cipher 4
9. The substitution cipher: possible keys 403,291,461,126,605,635,584,000,000 5
10. The substitution cipher: statistics 6
11. The substitution cipher: frequency analysis 7
12. Vigenère cipher
13. The Vigenère cipher 8
14. The Vigenère cipher 9
15. The Vigenère cipher 10
16. Breaking the Vigenère cipher
17. Breaking The Vigenère cipher 11
18. Breaking The Vigenère cipher 12
19. Enigma
20. Enigma 13
21. Enigma 14
22. Breaking Enigma 15
23. Modern ciphers
24. Modern cryptography • Confidentiality 16
25. Modern cryptography • Confidentiality • Key exchange 17
26. Modern cryptography • Confidentiality • Key exchange • Identity 18
27. Modern cryptography • Confidentiality • Key exchange • Identity • Authentication 19
28. Modern cryptography • Confidentiality • Key exchange • Identity • Authentication • Random number generation 20
29. Symmetric ciphers
30. Stream ciphers
31. A5/1
32. A5/1: implementation diagram 21
33. A5/1: register clocking 22
34. Stream cipher weaknesses • Keys must not be reused 23
35. Stream cipher weaknesses • Keys must not be reused • Easy for an attacker to modify a message 24
36. Stream cipher weaknesses • Keys must not be reused • Easy for an attacker to modify a message • Hard to partially decrypt messages 25
37. Block ciphers
38. AES
39. AES: 1 round • Substitute Bytes • Shift Rows • Mix Columns • Add Round Key 26
40. AES: Substitute Bytes 27
41. AES: Shift Rows 28
42. AES: Mix Columns 29
43. AES: Add Round Key 30
44. Modes of operation
45. ECB
46. ECB 31
47. ECB: the ECB penguin 1By Larry Ewing lewing@isc.tamu.edu with The GIMP 32
48. CBC
49. CBC 33
50. CTR
51. CTR 34
52. GCM
53. GCM 35
54. Asymetric ciphers
55. Public key cryptography
56. RSA
57. RSA • (me)d ≡ m (mod n) 36
58. RSA • (me)d ≡ m (mod n) • c ≡ me (mod n) 37
59. RSA • (me)d ≡ m (mod n) • c ≡ me (mod n) • cd ≡ (me)d ≡ m (mod n) 38
60. Identity verification
61. RSA: Message signatures • (md)e ≡ m (mod n) • s ≡ md (mod n) • se ≡ (md)e ≡ m (mod n) 39
62. Implementing Cryptography
63. Implementing Cryptography • Don’t 40
64. Implementing Cryptography • Don’t • Use existing implementations 41
65. Implementing Cryptography • Don’t • Use existing implementations • Bring in an expert 42
66. Implementing Cryptography in PHP
67. Implementing Cryptography in PHP • Halite + libsodium • https://github.com/paragonie/halite 43
68. Implementing Cryptography in PHP • Halite + libsodium • https://github.com/paragonie/halite • Defuse PHP encryption • https://github.com/defuse/php-encryption 44
69. Further reading • Simon Singh - The code book • http://simonsingh.net/The_Black_Chamber 45
70. Further reading • Simon Singh - The code book • http://simonsingh.net/The_Black_Chamber • Bruce Schneier • https://www.schneier.com 46
71. Further reading • Simon Singh - The code book • http://simonsingh.net/The_Black_Chamber • Bruce Schneier • https://www.schneier.com • https://github.com/gilfether/phpcrypt 47
72. Thanks • @giveupalready • https://github.com/carnage • https://joind.in/talk/d31d1 48
73. Cipher Challenge • The cipher challenge is now closed, but if you want to have a go anyway, the main text is now here • http://tiny.cc/0qq6by • @phpyorkshire 49