Foundations

Cryptography basics: the pieces the quantum threat rearranges

Symmetric ciphers, hashing, key exchange, and digital signatures: the four building blocks of secure communication, and which of them a quantum computer actually threatens.

Shor vs Grover: what breaks and what only weakens

Two quantum algorithms define the whole threat. Shor's breaks public-key cryptography outright; Grover's only weakens symmetric crypto, and is answered by using longer keys.

PQC algorithm families: lattice, hash-based, and the ones that failed

Post-quantum cryptography is built on different hard problems than RSA. Here are the main families, the NIST-standardized algorithms, and why some contenders were broken along the way.

Crypto-agility and hybrids: changing algorithms without a rewrite

The most durable outcome of a post-quantum migration is not any single algorithm but the ability to swap algorithms easily, and hybrids are how you deploy new ones safely in the meantime.