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# Joshua thijissen 1 6_alice & bob- pkc 101

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### Joshua thijissen 1 6_alice & bob- pkc 101

1. 1. Alice & Bob Public key cryptography 101 Mail.ru techforum - 24 april 2012 Moskow - Russiavrijdag 20 april 12
2. 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 2vrijdag 20 april 12
3. 3. An introduction into public key cryptography 3vrijdag 20 april 12
4. 4. Without this there would be no internet as we know today (really) 4vrijdag 20 april 12
5. 5. 5vrijdag 20 april 12
6. 6. Meet Alice, 5vrijdag 20 april 12
7. 7. Meet Alice, Hi Bob! and Bob. Hello Alice! 5vrijdag 20 april 12
8. 8. “bad” encryption algorithmshttp://www.ﬂickr.com/photos/dpwk/1714014449/in/pool-1621478@N23/ 6vrijdag 20 april 12
9. 9. “algorithm”: A = 1, B = 2, C = 3, ...., Z = 26 ‣ SUBSTITUTION SCHEME 7vrijdag 20 april 12
10. 10. “algorithm”: A = 1, B = 2, C = 3, ...., Z = 26 ciphertext: 19, 5, 3, 18, 5, 20 ‣ SUBSTITUTION SCHEME 7vrijdag 20 april 12
11. 11. “algorithm”: A = 1, B = 2, C = 3, ...., Z = 26 ciphertext: 19, 5, 3, 18, 5, 20 = S E C R E T ‣ SUBSTITUTION SCHEME 7vrijdag 20 april 12
12. 12. ‣ SUBSTITUTION SCHEME 8vrijdag 20 april 12
13. 13. ciphertext:  ‣ SUBSTITUTION SCHEME 8vrijdag 20 april 12
14. 14. ciphertext:  = WINGDINGS ‣ SUBSTITUTION SCHEME 8vrijdag 20 april 12
15. 15. “algorithm”: c = m + k mod 26 ‣ CAESARIAN CIPHER or CAESARIAN SHIFThttp://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg 9vrijdag 20 april 12
16. 16. “algorithm”: c = m + k mod 26 Message: C O D E ‣ CAESARIAN CIPHER or CAESARIAN SHIFThttp://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg 9vrijdag 20 april 12
17. 17. “algorithm”: c = m + k mod 26 Message: C O D E Ciphertext (key=1): DPEF ‣ CAESARIAN CIPHER or CAESARIAN SHIFThttp://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg 9vrijdag 20 april 12
18. 18. “algorithm”: c = m + k mod 26 Message: C O D E Ciphertext (key=1): DPEF Ciphertext (key=2): EQFG ‣ CAESARIAN CIPHER or CAESARIAN SHIFThttp://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg 9vrijdag 20 april 12
19. 19. “algorithm”: c = m + k mod 26 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 ‣ CAESARIAN CIPHER or CAESARIAN SHIFThttp://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg 9vrijdag 20 april 12
20. 20. “algorithm”: c = m + k mod 26 Message: C O D E Ciphertext (key=1): D P E F Ciphertext (key=0): C O D E Ciphertext (key=2): E Q F G Ciphertext (key=-1): B M C D ‣ CAESARIAN CIPHER or CAESARIAN SHIFThttp://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg 9vrijdag 20 april 12
21. 21. “algorithm”: c = m + k mod 26 Message: C O D E Ciphertext (key=1): D P E F Ciphertext (key=0): C O D E Ciphertext (key=2): E Q F G Ciphertext (key=26): C O D E Ciphertext (key=-1): B M C D ‣ CAESARIAN CIPHER or CAESARIAN SHIFThttp://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg 9vrijdag 20 april 12
22. 22. “algorithm”: c = m + k mod 26 Message: C O D E Ciphertext (key=1): D P E F Ciphertext (key=0): C O D E Ciphertext (key=2): E Q F G Ciphertext (key=26): C O D E Ciphertext (key=-1): B M C D Ciphertext (key=52): C O D E ‣ CAESARIAN CIPHER or CAESARIAN SHIFThttp://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg 9vrijdag 20 april 12
23. 23. ‣ FLAWS IN THESE CIPHERS 10vrijdag 20 april 12
24. 24. ➡ Key is too easy to guess. ‣ FLAWS IN THESE CIPHERS 10vrijdag 20 april 12
25. 25. ➡ Key is too easy to guess. ➡ Key has to be send to Bob. ‣ FLAWS IN THESE CIPHERS 10vrijdag 20 april 12
26. 26. ➡ Key is too easy to guess. ➡ Key has to be send to Bob. ➡ Deterministic. ‣ FLAWS IN THESE CIPHERS 10vrijdag 20 april 12
27. 27. ➡ Key is too easy to guess. ➡ Key has to be send to Bob. ➡ Deterministic. ➡ Prone to frequency analysis. ‣ FLAWS IN THESE CIPHERS 10vrijdag 20 april 12
28. 28. 11vrijdag 20 april 12
29. 29. ➡ The usage of every letter in the English (or any other language) can be represented by a percentage. 11vrijdag 20 april 12
30. 30. ➡ 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%. 11vrijdag 20 april 12
31. 31. ➡ 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%. ➡ ‘O’ is used 11.07% of the times in russian texts, the ‘Ъ’ only 0.02%. 11vrijdag 20 april 12
32. 32. 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."http://www.gutenberg.org/cache/epub/14082/pg14082.txt 12vrijdag 20 april 12
33. 33. A small bit of text can result in differences, but still there are some letters we can deduce.. ‣ “THE RAVEN”, FIRST PARAGRAPH 13vrijdag 20 april 12
34. 34. We can deduce almost all letters just without even CARING about the crypto algorithm used. ‣ “THE RAVEN”, ALL PARAGRAPHS 14vrijdag 20 april 12
35. 35. ‣ FLAWS IN THESE CIPHERS 15vrijdag 20 april 12
36. 36. ➡ Determinism and the ability to use frequency analysis are “bad things” ‣ FLAWS IN THESE CIPHERS 15vrijdag 20 april 12
37. 37. ‣ SYMMETRICAL ALGORITHMS 16vrijdag 20 april 12
38. 38. ➡ Previous examples were symmetrical encryptions. ‣ SYMMETRICAL ALGORITHMS 16vrijdag 20 april 12
39. 39. ➡ Previous examples were symmetrical encryptions. ➡ Same key is used for both encryption and decryption. ‣ SYMMETRICAL ALGORITHMS 16vrijdag 20 april 12
40. 40. ➡ Previous examples were symmetrical encryptions. ➡ Same key is used for both encryption and decryption. ➡ Good symmetrical encryptions: AES, Blowﬁsh, (3)DES ‣ SYMMETRICAL ALGORITHMS 16vrijdag 20 april 12
41. 41. ‣ THE PROBLEM WITH SYMMETRICAL ALGORITHMS 17vrijdag 20 april 12
42. 42. How does Alice send over the key securely to Bob? Everybody’s listening! ‣ THE PROBLEM WITH SYMMETRICAL ALGORITHMS 17vrijdag 20 april 12
43. 43. Another encryption system: Asymmetrical encryption or public key encryption. 18vrijdag 20 april 12
44. 44. Two keys instead of one: public key - available for everybody. Can be published on your blog. private key - For your eyes only! 19vrijdag 20 april 12
45. 45. ‣ USES 2 KEYS INSTEAD OF ONE: A KEYPAIR 20http://upload.wikimedia.org/wikipedia/commons/f/f9/Public_key_encryption.svgvrijdag 20 april 12
46. 46. It is NOT possible to decrypt the message with same key that is used to encrypt. 21vrijdag 20 april 12
47. 47. Encrypt with public key: - only private key (thus Alice) can decrypt. - message is only for Alice = encryption 22vrijdag 20 april 12
48. 48. Encrypt with public key: - only private key (thus Alice) can decrypt. - message is only for Alice = encryption Encrypt with private key: - only public key can decrypt. - message is guaranteed coming for Alice = signing 22vrijdag 20 april 12
49. 49. Symmetrical Asymmetrical ✓ quick. ✓ no need to send over the ✓ not resource intensive. (whole) key. ✓useful for small and large ✓ can be used for encryption messages. and validation (signing). ✗ need to send over the key ✗ very resource intensive. to the other side. ✗ only useful for small messages. 23vrijdag 20 april 12
50. 50. Use symmetrical encryption for the (large) message and encrypt the key used with an asymmetrical encryption method. 24vrijdag 20 april 12
51. 51. Hybrid ✓ quick ✓ not resource intensive ✓ useful for small and large messages ✓ safely exchange key data 25vrijdag 20 april 12
52. 52. Hybrid ✓ quick ✓ not resource intensive ✓ useful for small and large messages ✓ safely exchange key data + http://www.zastavki.com/pictures/1152x864/2008/Animals_Cats_Small_cat_005241_.jpg 25vrijdag 20 april 12
53. 53. But how does it work? 26vrijdag 20 april 12
54. 54. RSA 27vrijdag 20 april 12
55. 55. RSA Ron Rivest, Adi Shamir, Leonard Adleman 27vrijdag 20 april 12
56. 56. RSA Ron Rivest, Adi Shamir, Leonard Adleman 1978 27vrijdag 20 april 12
57. 57. RSA Ron Rivest, Adi Shamir, Leonard Adleman 1978 Pierre de Fermat, Leonard Euler 17th - 18th century 27vrijdag 20 april 12
58. 58. Public key encryption works on the premise that it is practically impossible to refactor a large number back into 2 separate prime numbers 28vrijdag 20 april 12
59. 59. 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... 28vrijdag 20 april 12
60. 60. 29vrijdag 20 april 12
61. 61. “large” number: 221 29vrijdag 20 april 12
62. 62. “large” number: 221 but we cannot calculate its prime factors without brute force. There is no “formula” (like e=mc2) 29vrijdag 20 april 12
63. 63. “large” number: 221 but we cannot calculate its prime factors without brute force. There is no “formula” (like e=mc2) (13 and 17) 29vrijdag 20 april 12
64. 64. 30vrijdag 20 april 12
65. 65. ➡ There is no proof that it’s impossible to refactor quickly (all tough it doesn’t look plausible) 30vrijdag 20 april 12
66. 66. ➡ 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). 30vrijdag 20 april 12
67. 67. The math behind the curtain 31vrijdag 20 april 12
68. 68. 32vrijdag 20 april 12
69. 69. ➡ p = (large) prime number 32vrijdag 20 april 12
70. 70. ➡ p = (large) prime number ➡ q = (large) prime number (but not too close to p) 32vrijdag 20 april 12
71. 71. ➡ p = (large) prime number ➡ q = (large) prime number (but not too close to p) ➡ n = p .q (bit length of the RSA key) 32vrijdag 20 april 12
72. 72. ➡ 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) 32vrijdag 20 april 12
73. 73. ➡ 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 32vrijdag 20 april 12
74. 74. ➡ 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 32vrijdag 20 april 12
75. 75. Step 1: select primes P and Q ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33vrijdag 20 april 12
76. 76. Step 1: select primes P and Q ‣ P = 11 ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33vrijdag 20 april 12
77. 77. Step 1: select primes P and Q ‣ P = 11 ‣ Q=3 ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33vrijdag 20 april 12
78. 78. Step 2: calculate N and Phi ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34vrijdag 20 april 12
79. 79. Step 2: calculate N and Phi ➡ N = P . Q = 11 . 3 = 33 ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34vrijdag 20 april 12
80. 80. Step 2: calculate N and Phi ➡ N = P . Q = 11 . 3 = 33 ➡ φ = (11-1) . (3-1) = 10 . 2 = 20 ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34vrijdag 20 april 12
81. 81. Step 2: calculate N and Phi ➡ N = P . Q = 11 . 3 = 33 ➡ φ = (11-1) . (3-1) = 10 . 2 = 20 33 decimal is 100001 in binary == 6 bit key ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34vrijdag 20 april 12
82. 82. Step 2: calculate N and Phi ➡ N = P . Q = 11 . 3 = 33 ➡ φ = (11-1) . (3-1) = 10 . 2 = 20 33 decimal is 100001 in binary == 6 bit key There are 20 co primes for 33 : φ(33) = 20 ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34vrijdag 20 april 12
83. 83. Step 3: ﬁnd e ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35vrijdag 20 april 12
84. 84. Step 3: ﬁnd e ‣ e=3 ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35vrijdag 20 april 12
85. 85. Step 3: ﬁnd e ‣ e=3 ‣ gcd(e, φ) = 1 ==> gcd(3, 20) = 1 ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35vrijdag 20 april 12
86. 86. Step 3: ﬁnd e ‣ e=3 ‣ gcd(e, φ) = 1 ==> gcd(3, 20) = 1 n 2 Fermat number: 2 + 1 ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35vrijdag 20 april 12
87. 87. Step 3: ﬁnd e ‣ e=3 ‣ gcd(e, φ) = 1 ==> gcd(3, 20) = 1 n 2 Fermat number: 2 + 1 Fermat prime: Fermat that is prime: 3, 5, 17, 257, 65537 Study shows that 98.5% of the time 65537 is used ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35vrijdag 20 april 12
88. 88. Step 4: ﬁnd d ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ? 36vrijdag 20 april 12
89. 89. Step 4: ﬁnd d ‣ Extended Euclidean Algorithm gives 7 ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ? 36vrijdag 20 april 12
90. 90. Step 4: ﬁnd d ‣ Extended Euclidean Algorithm gives 7 ‣ brute force: (e.d mod φ = 1) ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ? 36vrijdag 20 april 12
91. 91. Step 4: ﬁnd d ‣ Extended Euclidean Algorithm gives 7 ‣ brute force: (e.d mod φ = 1) 3 . 1 = 3 mod 20 = 3 3 . 6 = 18 mod 20 = 18 3 . 2 = 6 mod 20 = 6 3 . 7 = 21 mod 20 = 1 3 . 3 = 9 mod 20 = 9 3 . 8 = 24 mod 20 = 4 3 . 4 = 12 mod 20 = 12 3 . 9 = 27 mod 20 = 7 3 . 5 = 15 mod 20 = 15 3.10 = 30 mod 20 = 10 ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ? 36vrijdag 20 april 12
92. 92. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = 7 37vrijdag 20 april 12
93. 93. 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 37vrijdag 20 april 12
94. 94. The actual math is much more complex since we use very large numbers, but it all comes down to these (relatively simple) calculations.. 38vrijdag 20 april 12
95. 95. jthijssen@debian-jth:~\$ openssl rsa -text -noout -in server.key 39vrijdag 20 april 12
96. 96. 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 39vrijdag 20 april 12
97. 97. jthijssen@debian-jth:~\$ openssl rsa -text -noout -in server.key Private-Key: (256 bit) modulus: n 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) e privateExponent: 22:8f:fd:2b:82:90:30:96:36:d6:6c:73:09:5e:a9:87:73:6e: d 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 p prime2: 00:cf:8d:a1:3b:93:af:61:77:8f:c9:8f:1d:aa:8d:b4:4f exponent1: q 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 d mod (p-1) coefficient: 00:99:fa:de:80:d4:ee:f3:69:59:e5:8a:72:ad:e5:30:3d e mod (q-1) (inverse q) mod p 39vrijdag 20 april 12
98. 98. Encrypting a message: c = me mod n Decrypting a message: m = cd mod n 40vrijdag 20 april 12
99. 99. 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 41vrijdag 20 april 12
100. 100. Encrypting a message: private key = (n,d) = (33, 7): Decrypting a message: public key = (n,e) = (33, 3): m = 13, 20, 15, 5 c = 7, 26, 27,14 13^7 mod 33 = 7 7^3 mod 33 = 13 20^7 mod 33 = 26 26^3 mod 33 = 20 15^7 mod 33 = 27 27^3 mod 33 = 15 5^7 mod 33 = 14 14^3 mod 33 =5 c = 7, 26, 27,14 m = 13, 20, 15, 5 41vrijdag 20 april 12
101. 101. 42vrijdag 20 april 12
102. 102. ➡ A message is an “integer” 42vrijdag 20 april 12
103. 103. ➡ A message is an “integer” ➡ A message must be between 2 and n-1. 42vrijdag 20 april 12
104. 104. ➡ 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. 42vrijdag 20 april 12
105. 105. 43vrijdag 20 april 12
106. 106. ➡ Public Key Cryptography Standard #1 43vrijdag 20 april 12
107. 107. ➡ Public Key Cryptography Standard #1 ➡ Pads data with (random) bytes up to n bits in length (v1.5 or OAEP/v2.x). 43vrijdag 20 april 12
108. 108. ➡ 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) 43vrijdag 20 april 12
109. 109. 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 44vrijdag 20 april 12
110. 110. Practical applications of PKE 45vrijdag 20 april 12
111. 111. HTTPS 46vrijdag 20 april 12
112. 112. HTTPS ➡ HTTP encapsulated by TLS (previously SSL). 46vrijdag 20 april 12
113. 113. HTTPS ➡ HTTP encapsulated by TLS (previously SSL). ➡ More or less: an encryption layer on top of http. 46vrijdag 20 april 12
114. 114. HTTPS ➡ HTTP encapsulated by TLS (previously SSL). ➡ More or less: an encryption layer on top of http. ➡ Myth: HTTPS uses public key encryption for communication. 46vrijdag 20 april 12
115. 115. HTTPS ➡ HTTP encapsulated by TLS (previously SSL). ➡ More or less: an encryption layer on top of http. ➡ Myth: HTTPS uses public key encryption for communication. ➡ Fact: HTTPS uses public key encryption to SETUP communication. 46vrijdag 20 april 12
116. 116. 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) 47vrijdag 20 april 12
117. 117. HTTPS 48vrijdag 20 april 12
118. 118. HTTPS ➡ Browser sends over its encryption methods. 48vrijdag 20 april 12
119. 119. HTTPS ➡ Browser sends over its encryption methods. ➡ Server decides which one to use. 48vrijdag 20 april 12
120. 120. HTTPS ➡ Browser sends over its encryption methods. ➡ Server decides which one to use. ➡ Server send certiﬁcate(s). 48vrijdag 20 april 12
121. 121. HTTPS ➡ 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. 48vrijdag 20 april 12
122. 122. HTTPS ➡ 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. 48vrijdag 20 april 12
123. 123. HTTPS 49vrijdag 20 april 12
124. 124. HTTPS ➡ Thus: Public/private encryption is only used in establishing a secondary (better!?) encryption. 49vrijdag 20 april 12
125. 125. HTTPS ➡ 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) 49vrijdag 20 april 12
126. 126. HTTPS ➡ 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 49vrijdag 20 april 12
127. 127. http://change-your-ip.com/wp-content/uploads/image/nigerian_419_scam.jpghttp://torontoemerg.ﬁles.wordpress.com/2010/09/spam.gif 50vrijdag 20 april 12
128. 128. 51vrijdag 20 april 12
129. 129. Questions: 52vrijdag 20 april 12
130. 130. Questions: ➡ Did Bill really send this email? 52vrijdag 20 april 12
131. 131. Questions: ➡ Did Bill really send this email? ➡ Do we know for sure that nobody has read this email (before it came to us?) 52vrijdag 20 april 12
132. 132. Questions: ➡ 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? 52vrijdag 20 april 12
133. 133. Questions: ➡ 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! 52vrijdag 20 april 12
134. 134. Signing a message 53vrijdag 20 april 12
135. 135. Signing a message ➡ Signing a message means adding a signature that authenticates the validity of a message. 53vrijdag 20 april 12
136. 136. Signing a message ➡ 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. 53vrijdag 20 april 12
137. 137. Signing a message ➡ 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. 53vrijdag 20 april 12
138. 138. Signing a message http://en.wikipedia.org/wiki/File:Digital_Signature_diagram.svg 54vrijdag 20 april 12
139. 139. Introduction a pretty-good-privacy 55vrijdag 20 april 12
140. 140. Introduction a pretty-good-privacy ➡ GPG / PGP: Application for signing and/or encrypting data (or emails). 55vrijdag 20 april 12
141. 141. Introduction a pretty-good-privacy ➡ GPG / PGP: Application for signing and/or encrypting data (or emails). ➡ Try it yourself with Thunderbird’s Enigmail extension. 55vrijdag 20 april 12
142. 142. Introduction a pretty-good-privacy ➡ 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. 55vrijdag 20 april 12
143. 143. 56vrijdag 20 april 12
144. 144. ‣ Everybody can send emails that ONLY YOU can read. 56vrijdag 20 april 12
145. 145. ‣ Everybody can send emails that ONLY YOU can read. ‣ Everybody can verify that YOU have send the email and that it is authentic. 56vrijdag 20 april 12
146. 146. ‣ 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? 56vrijdag 20 april 12
147. 147. ‣ 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? 56vrijdag 20 april 12
148. 148. 57vrijdag 20 april 12
149. 149. SSH 58vrijdag 20 april 12
150. 150. SSH ➡ Public key authentication 58vrijdag 20 april 12
151. 151. SSH ➡ Public key authentication ➡ Because you suck at creating and/or remembering passwords 58vrijdag 20 april 12
152. 152. ➡ 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. 59vrijdag 20 april 12
153. 153. ➡ Domain Key Identiﬁed Mail (spam protection) ➡ BitCoin ➡ IPSEC / PKI ➡ DRM 60vrijdag 20 april 12
154. 154. Some words of wisdom: (free of charge) 61vrijdag 20 april 12
155. 155. 62vrijdag 20 april 12
156. 156. ➡ Don’t “invent” your own encryption. It will NOT be secure, and it WILL fail. 62vrijdag 20 april 12
157. 157. ➡ 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. 62vrijdag 20 april 12
158. 158. ➡ 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. 62vrijdag 20 april 12
159. 159. ➡ 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! 62vrijdag 20 april 12
160. 160. ➡ 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. 62vrijdag 20 april 12
161. 161. Questions? http://farm1.static.ﬂickr.com/73/163450213_18478d3aa6_d.jpg 63vrijdag 20 april 12
162. 162. Thank you Find me on twitter: @jaytaph Find me on email: jthijssen@noxlogic.nl Find me for blogs: www.adayinthelifeof.nl Find me for development and training: www.noxlogic.nl http://xkcd.com/153/ 64vrijdag 20 april 12