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4 articles with this tag.
Using a plain hash as a MAC, with tag = H(secret || message), is a classic mistake. A length-extension attack appends your own data and forges a valid tag without ever knowing the secret. Learn the attack on SHA-256, with runnable Python, and why HMAC exists.
11 min read
TLS 1.3 and the Signal Protocol both lean on the same small, elegant primitive to turn a shared secret into however many separate keys they actually need. Here's how HKDF's extract-then-expand design works.
8 min read
A hash alone can't prove a message wasn't tampered with. Anyone can recompute it. HMAC fixes that by mixing in a secret key, becoming one of the most quietly essential building blocks in TLS, SSH, and beyond.
8 min read
For nearly two decades, PBKDF2's answer to password cracking was simple: make every guess expensive by repeating a hash thousands of times. Here's how it works, and why memory-hard successors like Argon2 eventually surpassed it.
8 min read
