Cryptopals

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Solutions to the Matasano Cryptography Challenges

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Set 1: Basics

1. Conver hex to Base64
2. Fixed XOR
3. Single-byte XOR cipher
4. [Detect single-character XOR]
5. [Implement repeating-key XOR]
6. [Break repeating-key XOR]
7. [AES in ECB mode]
8. [Detect AES in ECB mode]

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Set 2: Block Crypto

9. [Implement PKCS#7 padding]
10. [Implement CBC mode]
11. [An ECB/CBC detection oracle]
12. [Byte-at-a-time ECB decryption(Simple)]
13. [ECB cut-and-paste]
14. [Byte-at-a-time ECB decryption(Harder)]
15. [PKCS#7 padding validation]
16. [CBC bitflipping attacks]

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Set 3: Block & Stream Crypto

17. [The CBC padding oracle]
18. [Implement CTR, the stream cipher mode]
19. [Break fixed-nonce CTR mode using substitutions]
20. [Break fixed-CTR statistically]
21. [Implement the MT19937 Mersenne Twister RNG]
22. [Crack an MT19937 seed]
23. [Clone an MT19937 RNG from its output]
24. [Create the MT19937 stream cipher and break it]

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Set 4: Stream Crypto and Randomness

25. [Break "random access read/write" AES CTR]
26. [CTR bitflipping]
27. [Recover the key from CBC with IV=Key]
28. [Implement a SHA-1 keyed MAC]
29. [Break a SHA-1 keyed MAC using length extension]
30. [Break an MD4 keyed MAC using length extension]
31. [Implement and break HMAC-SHA1 with an artificial timing leak]
32. [Break HMAC-SHA1 with a slightly less artificial timing leak]

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Set 5: Diffie-Hellman and Friends

33. [Implement Dffie-Hellman]
34. [Implement a MITM key-fixing attack on Diffie-Hellman with parameter injection]
35. [Implement DH with negotiated groups, and break with malicious "g" parameters]
36. [Implement Secure Remote Password (SRP)]
37. [Break SRP with a zero key]
38. [Offline dictionary attack on simplified SRP]
39. [Implement RSA]
40. [Implement an E=3 RSA Broadcast attack]

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Set 6: RSA and DSA

41. [Implement unpadded message recovery oracle]
42. [Bleichenbacher's e=3 RSA Attack]
43. [DSA key recovery from nonce]
44. [DSA nonce recovery repeated nonce]
45. [DSA parameter tampering]
46. [RSA parity oracle]
47. [Bleichenbacher's PKCS 1.5 Padding Oracle (Simple Case)]
48. [Bleichenbacher's PKCS 1.5 Padding Oracle (Complete Case)]

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Set 7: Hashes

49. [CBC-MAC Message Forgery]
50. [Hashing with CBC-MAC]
51. [Compression Ratio Side-Channel Attacks]
52. [Iterated Hash Function Multicollisions]
53. [Kelsey and Schneier's Expandable Messages]
54. [Kelsey and Kohno's Nostradamus Attacks]
55. [MD4 Collisions]
56. [RCC4 Single-Byte Biases]

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Set 8: Abstract Algebra

57. [Diffie-Hellman Revisted: Small Subgroup Confinement]
58. [Pollard's Mehtod for Catching Kangaroos]
59. [Elliptic Curve Diffie-Hellman and Invalid-Curve Attacks]
60. [Single-Coordinate Ladders and Insecure Twists]
61. [Duplicate-Signature Key Selection in ECDSA (and RSA)]
62. [Key-Recovery Attacks on ECDSA with Biased Nonces]
63. [Key-Recovery Attacks on GCM with Repeated Nonces]
64. [Key-Recovery Attacks on GCM with a Truncated MAC]
65. [Truncated-MAC GCM Revisited: Improving the Key-Recovery Attack via Ciphertext Length Extension]
66. [Exploiting Implementation Errors in Diffie-Hellman]

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