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HMAC-SHA512 generator

Compute HMAC-SHA512 for a message and secret key in your browser. HMAC-SHA512 gives 512-bit tags for the highest HMAC security margin.

Input

Enter the message and the secret key. 512-bit tags for high-assurance use.

The crypto library loads from a CDN on first use, then everything runs locally. Nothing you type is uploaded.
HMAC-SHA512 tag

The authentication tag appears below in hexadecimal.

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Maximum margin HMAC

HMAC-SHA512 produces 512-bit tags with 256-bit forgery resistance, the highest of the common HMACs. It is specified for high-assurance protocols and is the PRF inside PBKDF2-HMAC-SHA512 and TLS 1.2 cipher suites that need long-term security.

Truncation is fine

Many protocols truncate HMAC-SHA512 tags to 256 bits (for example, some token schemes). Truncating an HMAC tag is safe and standard practice; what matters is keeping enough bits, usually at least 128, for your threat model.

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HMAC-SHA512 FAQs

When do I need HMAC-SHA512?
High-assurance systems, long-lived tokens, and protocols already built on SHA-512. For typical webhooks HMAC-SHA256 is plenty; SHA-512 is the conservative upgrade.
How long is the tag?
128 hexadecimal characters (512 bits). Truncate to 64 hex chars if your protocol wants 256-bit tags.
Is it slower than HMAC-SHA256?
On 64-bit CPUs SHA-512 is often faster per byte than SHA-256, so HMAC-SHA512 can actually outperform HMAC-SHA256 on servers.
Key size guidance?
64 random bytes matches the 512-bit block structure nicely; 32 bytes is also fine. Avoid human-memorable passwords as keys.
Private computation?
Yes, the tag is computed locally in your browser; the key is never sent anywhere.
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