matasano

Matasano (now NCC Group) crypto challenges' (https://cryptopals.com) solutions

Briefly, these are a collection of exercises that demonstrate attacks on real-world cryptography. The exercises are derived from weaknesses in real-world systems and modern cryptographic constructions covering topics from symmetric ciphers such as AES (in a variety of modes), padding schemes such as PKCS#7, random number generators, hashing algorithmns, asymmetric ciphers such as DSA and RSA, a variety of famous attacks, and so on.

• Problem set 1
  • Convert hex to base64 and back
  • Fixed XOR
  • Single-character XOR Cipher
  • Detect single-character XOR
  • Repeating-key XOR Cipher
  • Break repeating-key XOR
  • AES in ECB Mode
  • Detecting ECB
• Problem set 2
  • Implement PKCS#7 padding
  • Implement CBC Mode
  • Write an oracle function and use it to detect ECB
  • Byte-at-a-time ECB decryption, Full control version
  • ECB cut-and-paste
  • Byte-at-a-time ECB decryption, Partial control version
  • PKCS#7 padding validation
  • CBC bit flipping
• Problem set 3
  • The CBC padding oracle
  • Implement CTR mode
  • Break fixed-nonce CTR mode using substitions
  • Break fixed-nonce CTR mode using stream cipher analysis
  • Implement the MT19937 Mersenne Twister RNG
  • "Crack" an MT19937 seed
  • Clone an MT19937 RNG from its output
  • Create the MT19937 stream cipher and break it
• Problem set 4
  • Break "random access read/write" AES CTR
  • CTR bit flipping
  • Recover the key from CBC with IV=Key
  • Implement a SHA-1 keyed MAC
  • Break a SHA-1 keyed MAC using length extension
  • Break an MD4 keyed MAC using length extension
  • Implement HMAC-SHA1 and break it with an artificial timing leak
  • Break HMAC-SHA1 with a slightly less artificial timing leak
• Problem set 5
  • Implement Diffie-Hellman
  • Implement a MITM key-fixing attack on Diffie-Hellman with parameter injection
  • Implement DH with negotiated groups, and break with malicious "g" parameters
  • Implement Secure Remote Password
  • Break SRP with a zero key
  • Offline dictionary attack on simplified SRP
  • Implement RSA
  • Implement an E=3 RSA Broadcast attack
• Problem set 6
  • Implement Unpadded Message Recovery Oracle
  • Bleichenbacher's e=3 RSA Attack
  • DSA Key Recovery From Nonce
  • DSA Nonce Recovery From Repeated Nonce
  • DSA Parameter Tampering
  • Decrypt RSA From One-Bit Oracle
  • Bleichenbacher's PKCS 1.5 Padding Oracle (Simple Case)
  • Bleichenbacher's PKCS 1.5 Padding Oracle (Complete)

License

This work is released to the public domain.