HMAC Explained: Keyed Hash Authentication Codes
How HMAC adds a secret key to hashing to prevent tampering, the construction algorithm, and common HMAC use cases.
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Tags: security, cryptography, hmac
HMAC: Hash-Based Message Authentication Code Explained HMAC (Hash-based Message Authentication Code) solves a problem that raw hash functions cannot: proving that a message came from a specific party and wasn't modified in transit. It does this by combining a secret key with the hash computation in a cryptographically sound way. Understanding HMAC matters because it's the foundation of JWT signatures (HS256), AWS request signing, API authentication, and dozens of other protocols. What Problem HMAC Solves A plain hash function like SHA-256 provides integrity: if you hash a file and the hash changes, the file changed. But it doesn't provide authentication: anyone can compute SHA-256(message) — the hash proves nothing about who created it. The naïve MAC attempt: — prepend a secret key to the…
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