Cryptography
// 7 published technical guides
Cryptography challenges range from classical ciphers to modern misuses of RSA, AES, and hashing. The goal is rarely to break math — it is to spot the implementation mistake.
› reference guides
- 01beginner
Classical Ciphers
Caesar, Vigenère, ROT13, and substitution — the ciphers CTF beginners meet first and how to crack them all.
- 02beginner
XOR Encoding
Understand XOR's role in CTF crypto — single-byte key recovery, repeating-key XOR, and the crib-drag attack.
- 03intermediate
RSA Basics
How RSA works mathematically, and the three beginner mistakes that make CTF RSA challenges solvable.
- 04intermediate
CBC Padding Oracle Attacks
Decrypt AES/DES ciphertexts and forge arbitrary encrypted messages by exploiting PKCS#7 padding validation errors in CBC mode.
- 05advanced
Diffie-Hellman Key Exchange Attacks
Break Diffie-Hellman implementations using small subgroup attacks, composite modulus factorizations, and Pohlig-Hellman discrete logarithms.
- 06intermediate
Hash Attacks & Length Extension
Exploit Merkle–Damgård hash functions (MD5, SHA-1, SHA-256) with length extension attacks and hash collision techniques.
- 07advanced
Elliptic Curve Cryptography Flaws
Exploit ECDSA nonce reuse, invalid curve attacks, and Pohlig-Hellman discrete logarithms on weak elliptic curves.