Cryptographic hash functions are the workhorse primitive of modern computing — every TLS handshake, git commit, password store, blockchain, and code signature relies on them. We walk what a hash function actually guarantees, the Merkle-Damgard versus sponge construction split that separates SHA-2 from SHA-3, the BLAKE3 parallel Merkle tree, the length-extension attack history, and what each function is good for.
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Hash Functions Explained