Alice & Bob: Public key cryptography 101 - FrOSCon 2012

Transcript

1. Alice & Bob FrOSCon - Bonn, Germany 25-26 August 2012 Public key cryptography 101
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
3. An introduction into public key cryptography 3
4. 4 Without this there would be no internet as we know today (really)
6. Meet Alice, and Bob. 5 Hi Bob! Hello Alice!
7. “bad” encryption algorithms 6 http://www.flickr.com/photos/dpwk/1714014449/in/pool-1621478@N23/
8. “algorithm”: A = 1, B = 2, C = 3, ...., Z = 26 ‣ SUBSTITUTION SCHEME 7
9. ciphertext: 12, 1, 13, 5 “algorithm”: A = 1, B = 2, C = 3, ...., Z = 26 ‣ SUBSTITUTION SCHEME 7
10. ciphertext: 12, 1, 13, 5 “algorithm”: A = 1, B = 2, C = 3, ...., Z = 26 = L A M E ‣ SUBSTITUTION SCHEME 7
11. 8 ‣ SUBSTITUTION SCHEME
12. 8 ciphertext:          ‣ SUBSTITUTION SCHEME
13. 8 ciphertext:          = W I N G D I N G S ‣ SUBSTITUTION SCHEME
14. “algorithm”: c = m + k mod 26 ‣ CAESARIAN CIPHER or CAESARIAN SHIFT 9 http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg
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
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
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
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
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
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
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
22. ‣ FLAWS IN THESE CIPHERS 10
23. ➡ Key is too easy to guess. ‣ FLAWS IN THESE CIPHERS 10
24. ➡ Key is too easy to guess. ➡ Key has to be send to Bob. ‣ FLAWS IN THESE CIPHERS 10
25. ➡ Key is too easy to guess. ➡ Key has to be send to Bob. ➡ Deterministic. ‣ FLAWS IN THESE CIPHERS 10
26. ➡ Key is too easy to guess. ➡ Key has to be send to Bob. ➡ Deterministic. ➡ Prone to frequency analysis. ‣ FLAWS IN THESE CIPHERS 10
28. ➡ The usage of every letter in the English (or any other language) can be represented by a percentage. 11
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
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
31. A small bit of text can result in differences, but still there are some letters we can deduce.. ‣ “THE RAVEN”, FIRST PARAGRAPH 13
32. We can deduce almost all letters just without even CARING about the crypto algorithm used. ‣ “THE RAVEN”, ALL PARAGRAPHS 14
33. ‣ FLAWS IN THESE CIPHERS 15
34. Determinism and the ability to apply frequency analysis are “bad things” ‣ FLAWS IN THESE CIPHERS 15
35. ‣ SYMMETRICAL ALGORITHMS 16
36. ➡ Previous examples were symmetrical encryptions. ‣ SYMMETRICAL ALGORITHMS 16
37. ➡ Previous examples were symmetrical encryptions. ➡ Same key is used for both encryption and decryption. ‣ SYMMETRICAL ALGORITHMS 16
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
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
40. ‣ THE PROBLEM WITH SYMMETRICAL ALGORITHMS 17
41. Q: How does Alice send over the key securely to Bob? Everybody’s listening! ‣ THE PROBLEM WITH SYMMETRICAL ALGORITHMS 17
42. Another encryption system: Asymmetrical encryption or public key encryption. 18
43. Two keys instead of one: public key - available for everybody. Can be published on your blog. private key - For your eyes only! 19
44. http://upload.wikimedia.org/wikipedia/commons/f/f9/Public_key_encryption.svg ‣ USES 2 KEYS INSTEAD OF ONE: A KEYPAIR 20
45. It is NOT possible to decrypt the message with same key that is used to encrypt. 21
46. Encrypt with public key: - only private key (thus Alice) can decrypt. - message is only for Alice = encryption 22
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
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
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!
50. Hybrid ✓ quick ✓ not resource intensive ✓ useful for small and large messages ✓ safely exchange key data 25
51. Hybrid ✓ quick ✓ not resource intensive ✓ useful for small and large messages ✓ safely exchange key data 25
52. + Hybrid ✓ quick ✓ not resource intensive ✓ useful for small and large messages ✓ safely exchange key data 25
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 =
54. But how does it work? 26
55. RSA 27
56. RSA Ron Rivest, Adi Shamir, Leonard Adleman 27
57. RSA Ron Rivest, Adi Shamir, Leonard Adleman 27 1978
58. RSA Ron Rivest, Adi Shamir, Leonard Adleman 27 1978 Pierre de Fermat, Leonard Euler 17th - 18th century
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
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
62. “large” number: 221 29
63. “large” number: 221 but we cannot calculate its prime factors without brute force. There is no “formula” (like e=mc2) 29
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
66. ➡ There is no proof that it’s impossible to refactor quickly (all tough it doesn’t look plausible) 30
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
68. 31 This is mathness! No, this is RSAAAA!
70. 32 ➡ p = (large) prime number
71. 32 ➡ p = (large) prime number ➡ q = (large) prime number (but not too close to p)
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)
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)
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
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
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
77. Step 1: select primes P and Q ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33
78. Step 1: select primes P and Q ‣ P = 11 ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33
79. Step 1: select primes P and Q ‣ P = 11 ‣ Q = 3 ‣ P = ? | Q = ? | N = ? | Phi = ? | e = ? | d = ? 33
80. Step 2: calculate N and Phi ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34
81. ➡ N = P . Q = 11 . 3 = 33 Step 2: calculate N and Phi ‣ P = 11 | Q = 3 | N = ? | Phi = ? | e = ? | d = ? 34
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
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
84. Step 3: find e ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35
85. Step 3: find e ‣ e = 3 ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = ? | d = ? 35
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
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
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
89. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ? Step 4: find d 36
90. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = ? Step 4: find d ‣ Extended Euclidean Algorithm gives 7 36
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
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
93. ‣ P = 11 | Q = 3 | N = 33 | Phi = 20 | e = 3 | d = 7 37
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
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
96. 39 jthijssen@debian-jth:~$ openssl rsa -text -noout -in server.key
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
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
99. Encrypting a message: c = me mod n Decrypting a message: m = cd mod n 40
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
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
103. ➡ A message is an “integer” 42
104. ➡ A message is an “integer” ➡ A message must be between 2 and n-1. 42
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
107. ➡ Public Key Cryptography Standard #1 43
108. ➡ Public Key Cryptography Standard #1 ➡ Pads data with (random) bytes up to n bits in length (v1.5 or OAEP/v2.x). 43
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
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
111. 45 Practical applications of PKE
112. HTTPS 46
113. ➡HTTP encapsulated by TLS (previously SSL). HTTPS 46
114. ➡HTTP encapsulated by TLS (previously SSL). ➡More or less: an encryption layer on top of http. HTTPS 46
115. ➡HTTP encapsulated by TLS (previously SSL). ➡More or less: an encryption layer on top of http. ➡Hybrid encryption. HTTPS 46
116. HTTPS 47
117. ➡Actual encryption methodology is decided by the browser and the server (highest possible encryption used). HTTPS 47
118. ➡Actual encryption methodology is decided by the browser and the server (highest possible encryption used). ➡Symmetric encryption (AES-256, others) HTTPS 47
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
120. HTTPS 48
121. ➡Key is exchanged in a public/private encrypted communication. HTTPS 48
122. ➡Key is exchanged in a public/private encrypted communication. ➡Which public key? HTTPS 48
123. ➡Key is exchanged in a public/private encrypted communication. ➡Which public key? ➡It is stored inside the server’s SSL certificate HTTPS 48
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)
125. HTTPS 50
126. ➡Browser sends over its encryption methods. HTTPS 50
127. ➡Browser sends over its encryption methods. ➡Server decides which one to use. HTTPS 50
128. ➡Browser sends over its encryption methods. ➡Server decides which one to use. ➡Server send certificate(s). HTTPS 50
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
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
131. HTTPS 51
132. ➡Thus: Public/private encryption is only used in establishing a secondary (better!?) encryption. HTTPS 51
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
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
135. http://torontoemerg.files.wordpress.com/2010/09/spam.gif http://change-your-ip.com/wp-content/uploads/image/nigerian_419_scam.jpg 52
137. Questions: 54
138. ➡ Did Bill really send this email? Questions: 54
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
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
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
142. Signing a message 55
143. ➡ Signing a message means adding a signature that authenticates the validity of a message. Signing a message 55
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
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
146. http://en.wikipedia.org/wiki/File:Digital_Signature_diagram.svg Signing a message 56
147. Introduction a pretty-good-privacy 57
148. ➡ GPG / PGP: Application for signing and/or encrypting data (or emails). Introduction a pretty-good-privacy 57
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
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
152. ‣ Everybody can send emails that ONLY YOU can read. 58
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
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
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
157. SSH 60
158. ➡ Public key authentication SSH 60
159. ➡ Public key authentication ➡ Because you suck at creating and/or remembering passwords SSH 60
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
161. ➡ Domain Key Identified Mail (spam protection) ➡ BitCoin ➡ IPSEC / PKI ➡ DRM 62
162. 63 Some words of wisdom: (free of charge)
164. ➡ Don’t “invent” your own encryption. It will NOT be secure, and it WILL fail. 64
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
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
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
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
169. http://farm1.static.flickr.com/73/163450213_18478d3aa6_d.jpg Questions? 65
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