Question 1

What is HMAC?

Accepted Answer

HMAC (Hash-based Message Authentication Code) is a mechanism for verifying both data integrity and authenticity using a cryptographic hash function and a secret key.

Question 2

What is HMAC-SHA256?

Accepted Answer

HMAC-SHA256 uses SHA-256 as the underlying hash function. It produces a 256-bit (32-byte) authentication code rendered as a 64-character hex string.

Question 3

When should I use HMAC?

Accepted Answer

Use HMAC when you need to verify that a message has not been tampered with and was sent by someone who knows the secret key. Common uses include API authentication and webhook verification.

Question 4

Is my secret key sent to a server?

Accepted Answer

No. All HMAC computation happens locally in your browser using the Web Crypto API. Your secret key and message never leave your device.

Question 5

What is the difference between HMAC and a regular hash?

Accepted Answer

A regular hash only provides integrity verification. HMAC adds authentication by incorporating a secret key, so only parties with the key can generate or verify the code.

Question 6

Can I use HMAC for password storage?

Accepted Answer

HMAC is not designed for password storage. Use dedicated password hashing algorithms like bcrypt or Argon2 instead.

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