Cryptography and Encryption Cheat Sheet

Cryptography is the science of securing information through mathematical transformations that render data unintelligible to unauthorized parties. It encompasses symmetric and asymmetric encryption, hashing, digital signatures, and key management—fundamental pillars of modern cybersecurity that protect data at rest, in transit, and during authentication. The distinction between encryption (reversible transformation) and hashing (one-way function) is critical: encryption provides confidentiality through decryption with the correct key, while hashing ensures integrity by producing fixed-size digests that cannot be reversed. Understanding cipher modes, key derivation, and attack vectors like timing leaks and nonce reuse is essential, as even strong algorithms become vulnerable when improperly implemented—cryptographic security depends as much on correct use as on algorithm strength.