Alice & Bob: Public key cryptography 101 - FrOSCon 2012

Transcript

1. Alice & Bob
   FrOSCon - Bonn, Germany
   25-26 August 2012
   Public key cryptography 101
   

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2. Joshua Thijssen / Netherlands
   Freelance consultant, developer and
   trainer @ NoxLogic / Techademy
   Development in PHP, Python, Perl,
   C, Java....
   Blog: http://adayinthelifeof.nl
   Email: jthijssen@noxlogic.nl
   Twitter: @jaytaph
   2
   

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3. An introduction into public key cryptography
   3
   

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4. 4
   Without this there would be
   no internet as we know today
   (really)
   

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5. View Slide

6. Meet Alice,
   and Bob.
   5
   Hi Bob!
   Hello Alice!
   

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7. “bad” encryption algorithms
   6
   http://www.flickr.com/photos/dpwk/1714014449/in/pool-1621478@N23/
   

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8. “algorithm”:
   A = 1, B = 2, C = 3, ...., Z = 26
   ‣ SUBSTITUTION SCHEME
   7
   

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9. ciphertext:
   12, 1, 13, 5
   “algorithm”:
   A = 1, B = 2, C = 3, ...., Z = 26
   ‣ SUBSTITUTION SCHEME
   7
   

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10. ciphertext:
    12, 1, 13, 5
    “algorithm”:
    A = 1, B = 2, C = 3, ...., Z = 26
    =
    L A M E
    ‣ SUBSTITUTION SCHEME
    7
    

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11. 8
    ‣ SUBSTITUTION SCHEME
    

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12. 8
    ciphertext:
            
    ‣ SUBSTITUTION SCHEME
    

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13. 8
    ciphertext:
            
    =
    W I N G D I N G S
    ‣ SUBSTITUTION SCHEME
    

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14. “algorithm”:
    c = m + k mod 26
    ‣ CAESARIAN CIPHER or CAESARIAN SHIFT
    9
    http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
    

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15. “algorithm”:
    c = m + k mod 26
    ‣ CAESARIAN CIPHER or CAESARIAN SHIFT
    9
    Message: C O D E
    http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
    

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16. “algorithm”:
    c = m + k mod 26
    ‣ CAESARIAN CIPHER or CAESARIAN SHIFT
    9
    Message: C O D E
    Ciphertext (key=1): D P E F
    http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
    

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17. “algorithm”:
    c = m + k mod 26
    ‣ CAESARIAN CIPHER or CAESARIAN SHIFT
    9
    Message: C O D E
    Ciphertext (key=1): D P E F
    Ciphertext (key=2): E Q F G
    http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
    

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18. “algorithm”:
    c = m + k mod 26
    ‣ CAESARIAN CIPHER or CAESARIAN SHIFT
    9
    Message: C O D E
    Ciphertext (key=1): D P E F
    Ciphertext (key=2): E Q F G
    Ciphertext (key=-1): B M C D
    http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
    

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19. “algorithm”:
    c = m + k mod 26
    ‣ CAESARIAN CIPHER or CAESARIAN SHIFT
    9
    Message: C O D E
    Ciphertext (key=1): D P E F
    Ciphertext (key=2): E Q F G
    Ciphertext (key=-1): B M C D
    Ciphertext (key=0): C O D E
    http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
    

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20. “algorithm”:
    c = m + k mod 26
    ‣ CAESARIAN CIPHER or CAESARIAN SHIFT
    9
    Message: C O D E
    Ciphertext (key=1): D P E F
    Ciphertext (key=2): E Q F G
    Ciphertext (key=-1): B M C D
    Ciphertext (key=0): C O D E
    Ciphertext (key=26): C O D E
    http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
    

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21. “algorithm”:
    c = m + k mod 26
    ‣ CAESARIAN CIPHER or CAESARIAN SHIFT
    9
    Message: C O D E
    Ciphertext (key=1): D P E F
    Ciphertext (key=2): E Q F G
    Ciphertext (key=-1): B M C D
    Ciphertext (key=0): C O D E
    Ciphertext (key=26): C O D E
    Ciphertext (key=52): C O D E
    http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
    

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22. ‣ FLAWS IN THESE CIPHERS
    10
    

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23. ➡ Key is too easy to guess.
    ‣ FLAWS IN THESE CIPHERS
    10
    

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24. ➡ Key is too easy to guess.
    ➡ Key has to be send to Bob.
    ‣ FLAWS IN THESE CIPHERS
    10
    

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25. ➡ Key is too easy to guess.
    ➡ Key has to be send to Bob.
    ➡ Deterministic.
    ‣ FLAWS IN THESE CIPHERS
    10
    

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26. ➡ Key is too easy to guess.
    ➡ Key has to be send to Bob.
    ➡ Deterministic.
    ➡ Prone to frequency analysis.
    ‣ FLAWS IN THESE CIPHERS
    10
    

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27. View Slide

28. ➡ The usage of every letter in the English (or
    any other language) can be represented by
    a percentage.
    11
    

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29. ➡ The usage of every letter in the English (or
    any other language) can be represented by
    a percentage.
    ➡ ‘E’ is used 12.7% of the times in english
    texts, the ‘Z’ only 0.074%.
    11
    

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30. http://www.gutenberg.org/cache/epub/14082/pg14082.txt
    Once upon a midnight dreary, while I pondered, weak and weary,
    Over many a quaint and curious volume of forgotten lore—
    While I nodded, nearly napping, suddenly there came a tapping,
    As of some one gently rapping—rapping at my chamber door.
    "'Tis some visitor," I muttered, "tapping at my chamber door—
    Only this and nothing more."
    12
    

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31. A small bit of text can result in differences, but still there are
    some letters we can deduce..
    ‣ “THE RAVEN”, FIRST PARAGRAPH
    13
    

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32. We can deduce almost all letters just without even CARING
    about the crypto algorithm used.
    ‣ “THE RAVEN”, ALL PARAGRAPHS
    14
    

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33. ‣ FLAWS IN THESE CIPHERS
    15
    

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34. Determinism and the ability to apply
    frequency analysis are “bad things”
    ‣ FLAWS IN THESE CIPHERS
    15
    

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35. ‣ SYMMETRICAL ALGORITHMS
    16
    

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36. ➡ Previous examples were symmetrical encryptions.
    ‣ SYMMETRICAL ALGORITHMS
    16
    

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37. ➡ Previous examples were symmetrical encryptions.
    ➡ Same key is used for both encryption and decryption.
    ‣ SYMMETRICAL ALGORITHMS
    16
    

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38. ➡ Previous examples were symmetrical encryptions.
    ➡ Same key is used for both encryption and decryption.
    ➡ Good symmetrical encryptions: AES, Blowfish, (3)DES.
    ‣ SYMMETRICAL ALGORITHMS
    16
    

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39. ➡ Previous examples were symmetrical encryptions.
    ➡ Same key is used for both encryption and decryption.
    ➡ Good symmetrical encryptions: AES, Blowfish, (3)DES.
    ➡ They are fast and secure.
    ‣ SYMMETRICAL ALGORITHMS
    16
    

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40. ‣ THE PROBLEM WITH SYMMETRICAL ALGORITHMS
    17
    

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41. Q: How does Alice send over the key securely
    to Bob? Everybody’s listening!
    ‣ THE PROBLEM WITH SYMMETRICAL ALGORITHMS
    17
    

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42. Another encryption system:
    Asymmetrical encryption or public key encryption.
    18
    

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43. Two keys instead of one:
    public key - available for everybody.
    Can be published on your blog.
    private key - For your eyes only!
    19
    

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44. http://upload.wikimedia.org/wikipedia/commons/f/f9/Public_key_encryption.svg
    ‣ USES 2 KEYS INSTEAD OF ONE: A KEYPAIR
    20
    

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45. It is NOT possible to decrypt the message
    with same key that is used to encrypt.
    21
    

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46. Encrypt with public key:
    - only private key (thus Alice) can decrypt.
    - message is only for Alice = encryption
    22
    

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47. Encrypt with public key:
    - only private key (thus Alice) can decrypt.
    - message is only for Alice = encryption
    22
    Encrypt with private key:
    - only public key can decrypt.
    - message is guaranteed coming for Alice = signing
    

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48. Symmetrical
    ✓ quick.
    ✓ not resource intensive.
    ✓ useful for small and large
    messages.
    ✗ need to send over the key
    to the other side.
    Asymmetrical
    ✓ no need to send over the
    (whole) key.
    ✓ can be used for encryption
    and validation (signing).
    ✗ very resource intensive.
    ✗ only useful for small messages.
    23
    

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49. A: Use symmetrical encryption for the (large)
    message and encrypt the key used with an
    asymmetrical encryption method.
    24
    Q: How does Alice send over the key securely
    to Bob? Everybody’s listening!
    

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50. Hybrid
    ✓ quick
    ✓ not resource intensive
    ✓ useful for small and large messages
    ✓ safely exchange key data
    25
    

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51. Hybrid
    ✓ quick
    ✓ not resource intensive
    ✓ useful for small and large messages
    ✓ safely exchange key data
    25
    

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52. +
    Hybrid
    ✓ quick
    ✓ not resource intensive
    ✓ useful for small and large messages
    ✓ safely exchange key data
    25
    

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53. +
    http://www.zastavki.com/pictures/1152x864/2008/Animals_Cats_Small_cat_005241_.jpg
    Hybrid
    ✓ quick
    ✓ not resource intensive
    ✓ useful for small and large messages
    ✓ safely exchange key data
    25
    =
    

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54. But how does it work?
    26
    

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55. RSA
    27
    

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56. RSA
    Ron Rivest, Adi Shamir, Leonard Adleman
    27
    

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57. RSA
    Ron Rivest, Adi Shamir, Leonard Adleman
    27
    1978
    

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58. RSA
    Ron Rivest, Adi Shamir, Leonard Adleman
    27
    1978
    Pierre de Fermat, Leonard Euler
    17th - 18th century
    

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59. Public key encryption works on the premise that it
    is practically impossible to refactor a large number
    back into 2 separate prime numbers
    28
    

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60. Public key encryption works on the premise that it
    is practically impossible to refactor a large number
    back into 2 separate prime numbers
    Prime number is only divisible by 1 and
    itself: 2, 3, 5, 7, 11, 13, 17, 19 etc...
    28
    

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61. View Slide

62. “large” number: 221
    29
    

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63. “large” number: 221
    but we cannot calculate its
    prime factors without brute force.
    There is no “formula” (like e=mc2)
    29
    

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64. “large” number: 221
    but we cannot calculate its
    prime factors without brute force.
    There is no “formula” (like e=mc2)
    (13 and 17)
    29
    

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65. View Slide

66. ➡ There is no proof that it’s impossible to refactor
    quickly (all tough it doesn’t look plausible)
    30
    

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67. ➡ There is no proof that it’s impossible to refactor
    quickly (all tough it doesn’t look plausible)
    ➡ Brute-force decrypting is always lurking around
    (quicker machines, better algorithms).
    30
    

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68. 31
    This is mathness!
    No, this is RSAAAA!
    

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69. View Slide

70. 32
    ➡ p = (large) prime number
    

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71. 32
    ➡ p = (large) prime number
    ➡ q = (large) prime number (but not too close to p)
    

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72. 32
    ➡ p = (large) prime number
    ➡ q = (large) prime number (but not too close to p)
    ➡ n = p . q (bit length of the RSA key)
    

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73. 32
    ➡ p = (large) prime number
    ➡ q = (large) prime number (but not too close to p)
    ➡ n = p . q (bit length of the RSA key)
    ➡ φ = (p-1) . (q-1) (the φ thingie is called phi)
    

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74. 32
    ➡ p = (large) prime number
    ➡ q = (large) prime number (but not too close to p)
    ➡ n = p . q (bit length of the RSA key)
    ➡ φ = (p-1) . (q-1) (the φ thingie is called phi)
    ➡ e = gcd(e, φ) = 1
    

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75. 32
    ➡ p = (large) prime number
    ➡ q = (large) prime number (but not too close to p)
    ➡ n = p . q (bit length of the RSA key)
    ➡ φ = (p-1) . (q-1) (the φ thingie is called phi)
    ➡ e = gcd(e, φ) = 1
    ➡ d = (d . e) mod φ = 1
    

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76. 32
    ➡ p = (large) prime number
    ➡ q = (large) prime number (but not too close to p)
    ➡ n = p . q (bit length of the RSA key)
    ➡ φ = (p-1) . (q-1) (the φ thingie is called phi)
    ➡ e = gcd(e, φ) = 1
    ➡ d = (d . e) mod φ = 1
    

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77. Step 1: select primes P and Q
    ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33
    

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78. Step 1: select primes P and Q
    ‣ P = 11
    ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33
    

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79. Step 1: select primes P and Q
    ‣ P = 11
    ‣ Q = 3
    ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33
    

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80. Step 2: calculate N and Phi
    ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34
    

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81. ➡ N = P . Q = 11 . 3 = 33
    Step 2: calculate N and Phi
    ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34
    

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82. ➡ N = P . Q = 11 . 3 = 33
    ➡ φ = (11-1) . (3-1) = 10 . 2 = 20
    Step 2: calculate N and Phi
    ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34
    

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83. ➡ N = P . Q = 11 . 3 = 33
    ➡ φ = (11-1) . (3-1) = 10 . 2 = 20
    Step 2: calculate N and Phi
    ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34
    33 decimal is 100001 in binary == 6 bit key
    

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84. Step 3: find e
    ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35
    

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85. Step 3: find e
    ‣ e = 3
    ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35
    

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86. Step 3: find e
    ‣ e = 3
    ‣ gcd(e, φ) = 1 ==> gcd(3, 20) = 1
    ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35
    

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87. Step 3: find e
    ‣ e = 3
    ‣ gcd(e, φ) = 1 ==> gcd(3, 20) = 1
    ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35
    Fermat number: 2 + 1
    2
    n
    

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88. Step 3: find e
    ‣ e = 3
    ‣ gcd(e, φ) = 1 ==> gcd(3, 20) = 1
    ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35
    Fermat number: 2 + 1
    2
    n
    Fermat prime: Fermat that is prime: 3, 5, 17, 257, 65537
    Study shows that 98.5% of the time 65537 is used
    

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89. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ?
    Step 4: find d
    36
    

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90. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ?
    Step 4: find d
    ‣ Extended Euclidean Algorithm gives 7
    36
    

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91. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ?
    Step 4: find d
    ‣ Extended Euclidean Algorithm gives 7
    ‣ brute force: (e.d mod φ = 1)
    36
    

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92. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ?
    Step 4: find d
    ‣ Extended Euclidean Algorithm gives 7
    ‣ brute force: (e.d mod φ = 1)
    3 . 1 = 3 mod 20 = 3
    3 . 2 = 6 mod 20 = 6
    3 . 3 = 9 mod 20 = 9
    3 . 4 = 12 mod 20 = 12
    3 . 5 = 15 mod 20 = 15
    3 . 6 = 18 mod 20 = 18
    3 . 7 = 21 mod 20 = 1
    3 . 8 = 24 mod 20 = 4
    3 . 9 = 27 mod 20 = 7
    3.10 = 30 mod 20 = 10
    36
    

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93. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = 7 37
    

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94. That’s it:
    ➡ public key = (n, e) = (33, 3)
    ➡ private key = (n, d) = (33, 7)
    ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = 7 37
    

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95. The actual math is much more complex since
    we use very large numbers, but it all comes
    down to these (relatively simple) calculations..
    38
    

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96. 39
    jthijssen@debian-jth:~$ openssl rsa -text -noout -in server.key
    

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97. 39
    jthijssen@debian-jth:~$ openssl rsa -text -noout -in server.key
    Private-Key: (256 bit)
    modulus:
    00:c2:d0:c4:1f:6f:78:16:82:d1:0c:dd:5a:af:de:f2:ff:31:c6:
    9b:3b:9f:e8:24:2a:5c:06:56:ea:d7:7c:c6:19
    publicExponent: 65537 (0x10001)
    privateExponent:
    22:8f:fd:2b:82:90:30:96:36:d6:6c:73:09:5e:a9:87:73:6e:
    2d:d4:d5:78:fc:3b:20:ea:0d:02:e5:2b:cb:3d
    prime1:
    00:f0:49:fd:91:18:01:53:92:8f:87:d7:2b:c8:19:7d:17
    prime2:
    00:cf:8d:a1:3b:93:af:61:77:8f:c9:8f:1d:aa:8d:b4:4f
    exponent1:
    00:e1:d8:c9:89:bc:84:52:a6:a8:5d:47:32:91:6a:d3:95
    exponent2:
    5a:88:b1:fa:d5:d9:db:8f:16:a6:5a:0a:1b:ba:42:1b
    coefficient:
    00:99:fa:de:80:d4:ee:f3:69:59:e5:8a:72:ad:e5:30:3d
    

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98. 39
    jthijssen@debian-jth:~$ openssl rsa -text -noout -in server.key
    n
    e
    d
    p
    q
    d mod (p-1)
    e mod (q-1)
    (inverse q) mod p
    Private-Key: (256 bit)
    modulus:
    00:c2:d0:c4:1f:6f:78:16:82:d1:0c:dd:5a:af:de:f2:ff:31:c6:
    9b:3b:9f:e8:24:2a:5c:06:56:ea:d7:7c:c6:19
    publicExponent: 65537 (0x10001)
    privateExponent:
    22:8f:fd:2b:82:90:30:96:36:d6:6c:73:09:5e:a9:87:73:6e:
    2d:d4:d5:78:fc:3b:20:ea:0d:02:e5:2b:cb:3d
    prime1:
    00:f0:49:fd:91:18:01:53:92:8f:87:d7:2b:c8:19:7d:17
    prime2:
    00:cf:8d:a1:3b:93:af:61:77:8f:c9:8f:1d:aa:8d:b4:4f
    exponent1:
    00:e1:d8:c9:89:bc:84:52:a6:a8:5d:47:32:91:6a:d3:95
    exponent2:
    5a:88:b1:fa:d5:d9:db:8f:16:a6:5a:0a:1b:ba:42:1b
    coefficient:
    00:99:fa:de:80:d4:ee:f3:69:59:e5:8a:72:ad:e5:30:3d
    

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99. Encrypting a message:
    c = me mod n
    Decrypting a message:
    m = cd mod n
    40
    

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100. Encrypting a message: private key = (n,d) = (33, 7):
     Decrypting a message: public key = (n,e) = (33, 3):
     m = 13, 20, 15, 5
     13^7 mod 33 = 7
     20^7 mod 33 = 26
     15^7 mod 33 = 27
     5^7 mod 33 = 14
     c = 7, 26, 27,14
     41
     

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101. Encrypting a message: private key = (n,d) = (33, 7):
     Decrypting a message: public key = (n,e) = (33, 3):
     m = 13, 20, 15, 5
     13^7 mod 33 = 7
     20^7 mod 33 = 26
     15^7 mod 33 = 27
     5^7 mod 33 = 14
     c = 7, 26, 27,14
     41
     c = 7, 26, 27,14
     7^3 mod 33 = 13
     26^3 mod 33 = 20
     27^3 mod 33 = 15
     14^3 mod 33 =5
     m = 13, 20, 15, 5
     

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102. View Slide

103. ➡ A message is an “integer”
     42
     

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104. ➡ A message is an “integer”
     ➡ A message must be between 2 and n-1.
     42
     

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105. ➡ A message is an “integer”
     ➡ A message must be between 2 and n-1.
     ➡ Deterministic, so we must use a padding
     scheme to make it non-deterministic.
     42
     

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106. View Slide

107. ➡ Public Key Cryptography Standard #1
     43
     

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108. ➡ Public Key Cryptography Standard #1
     ➡ Pads data with (random) bytes up to n bits
     in length (v1.5 or OAEP/v2.x).
     43
     

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109. ➡ Public Key Cryptography Standard #1
     ➡ Pads data with (random) bytes up to n bits
     in length (v1.5 or OAEP/v2.x).
     ➡ Got it flaws and weaknesses too. Always
     use the latest available version (v2.1)
     43
     

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110. Data = 4E636AF98E40F3ADCFCCB698F4E80B9F
     The encoded message block, EMB, after encoding but before encryption, with random
     padding bytes shown in green:
     0002257F48FD1F1793B7E5E02306F2D3228F5C95ADF5F31566729F132AA12009
     E3FC9B2B475CD6944EF191E3F59545E671E474B555799FE3756099F044964038
     B16B2148E9A2F9C6F44BB5C52E3C6C8061CF694145FAFDB24402AD1819EACEDF
     4A36C6E4D2CD8FC1D62E5A1268F496004E636AF98E40F3ADCFCCB698F4E80B9F
     After RSA encryption, the output is:
     3D2AB25B1EB667A40F504CC4D778EC399A899C8790EDECEF062CD739492C9CE5
     8B92B9ECF32AF4AAC7A61EAEC346449891F49A722378E008EFF0B0A8DBC6E621
     EDC90CEC64CF34C640F5B36C48EE9322808AF8F4A0212B28715C76F3CB99AC7E
     609787ADCE055839829E0142C44B676D218111FFE69F9D41424E177CBA3A435B
     http://www.di-mgt.com.au/rsa_alg.html#pkcs1schemes 44
     

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111. 45
     Practical applications of PKE
     

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112. HTTPS
     46
     

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113. ➡HTTP encapsulated by TLS (previously SSL).
     HTTPS
     46
     

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114. ➡HTTP encapsulated by TLS (previously SSL).
     ➡More or less: an encryption layer on top of http.
     HTTPS
     46
     

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115. ➡HTTP encapsulated by TLS (previously SSL).
     ➡More or less: an encryption layer on top of http.
     ➡Hybrid encryption.
     HTTPS
     46
     

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116. HTTPS
     47
     

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117. ➡Actual encryption methodology is decided by
     the browser and the server (highest possible
     encryption used).
     HTTPS
     47
     

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118. ➡Actual encryption methodology is decided by
     the browser and the server (highest possible
     encryption used).
     ➡Symmetric encryption (AES-256, others)
     HTTPS
     47
     

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119. ➡Actual encryption methodology is decided by
     the browser and the server (highest possible
     encryption used).
     ➡Symmetric encryption (AES-256, others)
     ➡But both sides needs the same key, so we
     have the same problem as before: how do we
     send over the key?
     HTTPS
     47
     

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120. HTTPS
     48
     

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121. ➡Key is exchanged in a public/private encrypted
     communication.
     HTTPS
     48
     

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122. ➡Key is exchanged in a public/private encrypted
     communication.
     ➡Which public key?
     HTTPS
     48
     

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123. ➡Key is exchanged in a public/private encrypted
     communication.
     ➡Which public key?
     ➡It is stored inside the server’s SSL certificate
     HTTPS
     48
     

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124. 49
     jthijssen@debian-jth:~$ openssl x509 -text -noout -in github.pem
     Certificate:
     Data:
     Version: 3 (0x2)
     Serial Number:
     0e:77:76:8a:5d:07:f0:e5:79:59:ca:2a:9d:50:82:b5
     Signature Algorithm: sha1WithRSAEncryption
     Issuer: C=US, O=DigiCert Inc, OU=www.digicert.com, CN=DigiCert High Assurance EV CA-1
     Validity
     Not Before: May 27 00:00:00 2011 GMT
     Not After : Jul 29 12:00:00 2013 GMT
     Subject: businessCategory=Private Organization/1.3.6.1.4.1.311.60.2.1.3=US/
     1.3.6.1.4.1.311.60.2.1.2=California/serialNumber=C3268102, C=US, ST=California, L=San Francisco, O=GitHub, Inc.,
     CN=github.com
     Subject Public Key Info:
     Public Key Algorithm: rsaEncryption
     RSA Public Key: (2048 bit)
     Modulus (2048 bit):
     00:ed:d3:89:c3:5d:70:72:09:f3:33:4f:1a:72:74:
     d9:b6:5a:95:50:bb:68:61:9f:f7:fb:1f:19:e1:da:
     04:31:af:15:7c:1a:7f:f9:73:af:1d:e5:43:2b:56:
     09:00:45:69:4a:e8:c4:5b:df:c2:77:52:51:19:5b:
     d1:2b:d9:39:65:36:a0:32:19:1c:41:73:fb:32:b2:
     3d:9f:98:ec:82:5b:0b:37:64:39:2c:b7:10:83:72:
     cd:f0:ea:24:4b:fa:d9:94:2e:c3:85:15:39:a9:3a:
     f6:88:da:f4:27:89:a6:95:4f:84:a2:37:4e:7c:25:
     78:3a:c9:83:6d:02:17:95:78:7d:47:a8:55:83:ee:
     13:c8:19:1a:b3:3c:f1:5f:fe:3b:02:e1:85:fb:11:
     66:ab:09:5d:9f:4c:43:f0:c7:24:5e:29:72:28:ce:
     d4:75:68:4f:24:72:29:ae:39:28:fc:df:8d:4f:4d:
     83:73:74:0c:6f:11:9b:a7:dd:62:de:ff:e2:eb:17:
     e6:ff:0c:bf:c0:2d:31:3b:d6:59:a2:f2:dd:87:4a:
     48:7b:6d:33:11:14:4d:34:9f:32:38:f6:c8:19:9d:
     f1:b6:3d:c5:46:ef:51:0b:8a:c6:33:ed:48:61:c4:
     1d:17:1b:bd:7c:b6:67:e9:39:cf:a5:52:80:0a:f4:
     ea:cd
     Exponent: 65537 (0x10001)
     

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125. HTTPS
     50
     

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126. ➡Browser sends over its encryption methods.
     HTTPS
     50
     

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127. ➡Browser sends over its encryption methods.
     ➡Server decides which one to use.
     HTTPS
     50
     

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128. ➡Browser sends over its encryption methods.
     ➡Server decides which one to use.
     ➡Server send certificate(s).
     HTTPS
     50
     

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129. ➡Browser sends over its encryption methods.
     ➡Server decides which one to use.
     ➡Server send certificate(s).
     ➡Client sends “session key” encrypted by the
     public key found in the server certificate.
     HTTPS
     50
     

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130. ➡Browser sends over its encryption methods.
     ➡Server decides which one to use.
     ➡Server send certificate(s).
     ➡Client sends “session key” encrypted by the
     public key found in the server certificate.
     ➡Server and client uses the “session key” for
     symmetrical encryption.
     HTTPS
     50
     

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131. HTTPS
     51
     

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132. ➡Thus: Public/private encryption is only used in
     establishing a secondary (better!?) encryption.
     HTTPS
     51
     

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133. ➡Thus: Public/private encryption is only used in
     establishing a secondary (better!?) encryption.
     ➡SSL/TLS is a separate talk (it’s way more complex
     as this)
     HTTPS
     51
     

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134. ➡Thus: Public/private encryption is only used in
     establishing a secondary (better!?) encryption.
     ➡SSL/TLS is a separate talk (it’s way more complex
     as this)
     ➡http://www.moserware.com/2009/06/first-few-
     milliseconds-of-https.html
     HTTPS
     51
     

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135. http://torontoemerg.files.wordpress.com/2010/09/spam.gif
     http://change-your-ip.com/wp-content/uploads/image/nigerian_419_scam.jpg
     52
     

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136. View Slide

137. Questions:
     54
     

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138. ➡ Did Bill really send this email?
     Questions:
     54
     

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139. ➡ Did Bill really send this email?
     ➡ Do we know for sure that nobody has read
     this email (before it came to us?)
     Questions:
     54
     

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140. ➡ Did Bill really send this email?
     ➡ Do we know for sure that nobody has read
     this email (before it came to us?)
     ➡ Do we know for sure that the contents of
     the message isn’t tampered with?
     Questions:
     54
     

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141. ➡ Did Bill really send this email?
     ➡ Do we know for sure that nobody has read
     this email (before it came to us?)
     ➡ Do we know for sure that the contents of
     the message isn’t tampered with?
     ➡ We use signing!
     Questions:
     54
     

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142. Signing a message
     55
     

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143. ➡ Signing a message means adding a signature
     that authenticates the validity of a message.
     Signing a message
     55
     

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144. ➡ Signing a message means adding a signature
     that authenticates the validity of a message.
     ➡ Like md5 or sha1, so when the message
     changes, so will the signature.
     Signing a message
     55
     

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145. ➡ Signing a message means adding a signature
     that authenticates the validity of a message.
     ➡ Like md5 or sha1, so when the message
     changes, so will the signature.
     ➡ This works on the premise that Alice and
     only Alice has the private key that can
     create the signature.
     Signing a message
     55
     

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146. http://en.wikipedia.org/wiki/File:Digital_Signature_diagram.svg
     Signing a message
     56
     

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147. Introduction a pretty-good-privacy
     57
     

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148. ➡ GPG / PGP: Application for signing and/or
     encrypting data (or emails).
     Introduction a pretty-good-privacy
     57
     

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149. ➡ GPG / PGP: Application for signing and/or
     encrypting data (or emails).
     ➡ Try it yourself with Thunderbird’s Enigmail
     extension.
     Introduction a pretty-good-privacy
     57
     

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150. ➡ GPG / PGP: Application for signing and/or
     encrypting data (or emails).
     ➡ Try it yourself with Thunderbird’s Enigmail
     extension.
     ➡ Public keys can be send / found on PGP-
     servers so you don’t need to send your
     keys to everybody all the time.
     Introduction a pretty-good-privacy
     57
     

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151. View Slide

152. ‣ Everybody can send emails that ONLY YOU can read.
     58
     

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153. ‣ Everybody can send emails that ONLY YOU can read.
     ‣ Everybody can verify that YOU have send the email
     and that it is authentic.
     58
     

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154. ‣ Everybody can send emails that ONLY YOU can read.
     ‣ Everybody can verify that YOU have send the email
     and that it is authentic.
     ‣ Why is this not the standard?
     58
     

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155. ‣ Everybody can send emails that ONLY YOU can read.
     ‣ Everybody can verify that YOU have send the email
     and that it is authentic.
     ‣ Why is this not the standard?
     ‣ No really, why isn’t it the standard?
     58
     

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156. View Slide

157. SSH
     60
     

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158. ➡ Public key authentication
     SSH
     60
     

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159. ➡ Public key authentication
     ➡ Because you suck at creating and/or
     remembering passwords
     SSH
     60
     

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160. ➡ Run ssh-keygen
     ➡ copy id_rsa.pub over to server’s ~/.ssh/
     authorized_keys
     ➡ Easy for tools / scripts to connect
     ➡ Easy for you (no remembering passwords)
     ➡ More fine grained security model.
     61
     

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161. ➡ Domain Key Identified Mail
     (spam protection)
     ➡ BitCoin
     ➡ IPSEC / PKI
     ➡ DRM
     62
     

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162. 63
     Some words of wisdom:
     (free of charge)
     

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163. View Slide

164. ➡ Don’t “invent” your own encryption. It will
     NOT be secure, and it WILL fail.
     64
     

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165. ➡ Don’t “invent” your own encryption. It will
     NOT be secure, and it WILL fail.
     ➡ Encryption is as strong as the weakest link,
     which 9 out of 10 times will be you.
     64
     

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166. ➡ Don’t “invent” your own encryption. It will
     NOT be secure, and it WILL fail.
     ➡ Encryption is as strong as the weakest link,
     which 9 out of 10 times will be you.
     ➡ Encryptions evolve. Do not use today what
     you used 10 years ago.
     64
     

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167. ➡ Don’t “invent” your own encryption. It will
     NOT be secure, and it WILL fail.
     ➡ Encryption is as strong as the weakest link,
     which 9 out of 10 times will be you.
     ➡ Encryptions evolve. Do not use today what
     you used 10 years ago.
     ➡ Every encryption will become obsolete!
     64
     

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168. ➡ Don’t “invent” your own encryption. It will
     NOT be secure, and it WILL fail.
     ➡ Encryption is as strong as the weakest link,
     which 9 out of 10 times will be you.
     ➡ Encryptions evolve. Do not use today what
     you used 10 years ago.
     ➡ Every encryption will become obsolete!
     ➡ Always follow the best practices.
     64
     

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169. http://farm1.static.flickr.com/73/163450213_18478d3aa6_d.jpg
     Questions?
     65
     

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170. Thank you
     66
     Find me on twitter: @jaytaph
     Find me for development and training: www.noxlogic.nl
     Find me on email: jthijssen@noxlogic.nl
     Find me for blogs: www.adayinthelifeof.nl
     

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