HMAC Generator
Compute an HMAC with MD5, SHA-1, SHA-224/256/384/512 or RIPEMD-160. Key and message as text, hex or Base64; hex, Base64 or Base64URL output. Runs in your browser.
HMAC (hash-based message authentication code) combines a secret key with a hash function to prove a message is authentic and unchanged. It is the mechanism behind API request signing, webhooks and JWT HS256 tokens. This tool computes HMACs with seven hash functions, taking the key and message as text, hex or Base64, all in your browser.
How to use this tool
- Enter the message and the secret key.
- Set how each is encoded (text, hex or Base64).
- Choose the hash algorithm.
- Copy the HMAC, or paste an expected value to check it matches.
Formula
HMAC(K, m) = H((K ⊕ opad) ∥ H((K ⊕ ipad) ∥ m)), where H is the chosen hash and ipad/opad are fixed padding constants. The key is hashed first if it is longer than the block size.
Example
With the key "Jefe" and the message "what do ya want for nothing?", HMAC-SHA256 is 5bdcc146bf60754e6a042426089575c75a003f089d2739839dec58b964ec3843 — RFC 4231 test case 2.
Frequently asked questions
Why HMAC instead of just hashing key + message?
A plain hash of key followed by message is vulnerable to length-extension attacks. HMAC’s nested construction with inner and outer padding prevents that.
Which algorithm should I use?
HMAC-SHA256 is the common default and is secure. Avoid HMAC-MD5 and HMAC-SHA1 for new systems, though they appear in older protocols.
How do I verify a signature?
Compute the HMAC of the received message with the shared key and compare it to the signature sent. Paste the expected value into the compare box to check.
Sources
Last updated:
Page address with these inputs: https://kakao.mobile/tools/hmac-generator/
Cite or embed this tool
kakaoCalc. (2026, November 8). HMAC Generator. https://kakao.mobile/tools/hmac-generator/
“HMAC Generator.” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/hmac-generator/.
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