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HMAC generator and verifier
Keyed MACs over any text — SHA-1, SHA-256, SHA-384, SHA-512 through WebCrypto, keys as text, hex, or base64. RFC 4231-exact, computed in your tab.
- No encryption, only authentication — an HMAC proves the message and key match, it hides nothing.
- The shared secret lives in this tab’s memory while you work — nothing is sent or stored, a browser tab cannot guarantee the memory is zeroized after, and browser extensions can read page content.
- The comparison here is for pasted digests, not live secrets — production verifiers compare in constant time.
- SHA-1 HMAC still resists collision attacks in this role, but new systems pick SHA-256 or better.
Nothing in yet
Paste, drop, or type to begin. Everything stays on this device.
key + message, then compute