Cryptography

Cryptography, as Wikipedia describes it, is the practice and study of techniques for secure communication in presence of adversarial behaviour.

In CTFs, crypto challenges include a wide variety of topics, but some topics are encountered more than the other:

Understanding and breaking cryptography is a pretty nifty skill to have under one’s belt.

• RSA encryption scheme and related attacks
• Various ciphers like substitution cipher, vignere cipher, rail-fence cipher, ROT13, One Time Pad etc.
• AES encryption
• Diffie-Hellman Key Exchange algo.
• Hashing schemes like SHA256.
• Elliptic Curve Cryptography
• Lattices
• Post-Quantum Crypto

Note that the latter topics are more advanced.

A background in mathematics helps, if you find discrete mathematics interesting, you will enjoy Asymmetric encryption schemes 😄

Resources

• Cryptohack
• Cryptopals
• Mystery Twister C3
• CyberChef