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
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2. Introduction
   

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3. Cryptography is HARD
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4. Historic ciphers
   

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5. The ceasar shift
   

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6. The ceasar shift
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7. The substitution cipher
   

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8. The substitution cipher
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9. The substitution cipher: possible keys
   403,291,461,126,605,635,584,000,000
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10. The substitution cipher: statistics
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11. The substitution cipher: frequency analysis
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12. Vigenère cipher
    

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13. The Vigenère cipher
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14. The Vigenère cipher
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15. The Vigenère cipher
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16. Breaking the Vigenère cipher
    

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17. Breaking The Vigenère cipher
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18. Breaking The Vigenère cipher
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19. Enigma
    

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20. Enigma
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21. Enigma
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22. Breaking Enigma
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23. Modern ciphers
    

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24. Modern cryptography
    • Confidentiality
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25. Modern cryptography
    • Confidentiality
    • Key exchange
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26. Modern cryptography
    • Confidentiality
    • Key exchange
    • Identity
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27. Modern cryptography
    • Confidentiality
    • Key exchange
    • Identity
    • Authentication
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28. Modern cryptography
    • Confidentiality
    • Key exchange
    • Identity
    • Authentication
    • Random number generation
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29. Symmetric ciphers
    

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30. Stream ciphers
    

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31. A5/1
    

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32. A5/1: implementation diagram
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33. A5/1: register clocking
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34. Stream cipher weaknesses
    • Keys must not be reused
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35. Stream cipher weaknesses
    • Keys must not be reused
    • Easy for an attacker to modify a message
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36. Stream cipher weaknesses
    • Keys must not be reused
    • Easy for an attacker to modify a message
    • Hard to partially decrypt messages
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37. Block ciphers
    

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38. AES
    

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39. AES: 1 round
    • Substitute Bytes
    • Shift Rows
    • Mix Columns
    • Add Round Key
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40. AES: Substitute Bytes
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41. AES: Shift Rows
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42. AES: Mix Columns
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43. AES: Add Round Key
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44. Modes of operation
    

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45. ECB
    

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46. ECB
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47. ECB: the ECB penguin
    1By Larry Ewing lewing@isc.tamu.edu with The GIMP
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48. CBC
    

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49. CBC
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50. CTR
    

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51. CTR
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52. GCM
    

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53. GCM
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54. Asymetric ciphers
    

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55. Public key cryptography
    

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56. RSA
    

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57. RSA
    • (me)d ≡ m (mod n)
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58. RSA
    • (me)d ≡ m (mod n)
    • c ≡ me (mod n)
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59. RSA
    • (me)d ≡ m (mod n)
    • c ≡ me (mod n)
    • cd ≡ (me)d ≡ m (mod n)
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60. Identity verification
    

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61. RSA: Message signatures
    • (md)e ≡ m (mod n)
    • s ≡ md (mod n)
    • se ≡ (md)e ≡ m (mod n)
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62. Implementing Cryptography
    

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63. Implementing Cryptography
    • Don’t
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64. Implementing Cryptography
    • Don’t
    • Use existing implementations
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65. Implementing Cryptography
    • Don’t
    • Use existing implementations
    • Bring in an expert
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66. Implementing Cryptography in PHP
    

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67. Implementing Cryptography in PHP
    • Halite + libsodium
    • https://github.com/paragonie/halite
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68. Implementing Cryptography in PHP
    • Halite + libsodium
    • https://github.com/paragonie/halite
    • Defuse PHP encryption
    • https://github.com/defuse/php-encryption
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69. Further reading
    • Simon Singh - The code book
    • http://simonsingh.net/The_Black_Chamber
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70. Further reading
    • Simon Singh - The code book
    • http://simonsingh.net/The_Black_Chamber
    • Bruce Schneier
    • https://www.schneier.com
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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
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72. Thanks
    • @giveupalready
    • https://github.com/carnage
    • https://joind.in/talk/d31d1
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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
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