Hash-Based Message Authentication Code (HMAC) - Glossary (2024)

FAQs

What is the hashed message authentication code HMAC __________? ›

Hash-based message authentication code (or HMAC) is a cryptographic authentication technique that uses a hash function and a secret key. With HMAC, you can achieve authentication and verify that data is correct and authentic with shared secrets, as opposed to approaches that use signatures and asymmetric cryptography.

In a MAC algorithm, the tag is typically computed by applying a cryptographic function directly to the message and the secret key. In contrast, HMAC uses a more complex construction that involves two passes of the hash function, along with the use of inner and outer padding.

Hash-Based Message Authentication Code (HMAC)

HMACSHA256 is a type of keyed hash algorithm that is constructed from the SHA-256 hash function and used as a Hash-based Message Authentication Code (HMAC).

The secret cryptographic key is what enables a user to make an encrypted message readable after it has been encrypted by an algorithm. In an HMAC transaction, the client and server must agree on the secret key. This provides a way to decode messages, which must stay secret, to maintain the transaction's integrity.

The HMAC process ensures that your data isn't open to attacks and safeguards its integrity. When the HMAC process is finished the message becomes permanently hashed, meaning it can only be accessed and unlocked with the right secret key.

HMAC stands for Keyed-Hashing for Message Authentication. It's a message authentication code obtained by running a cryptographic hash function (like MD5, SHA1, and SHA256) over the data (to be authenticated) and a shared secret key. HMAC is specified in RFC 2104. HMACs are almost similar to digital signatures.

A message authentication code uses a single key with the message and hashes it to validate the message's sender identity and ensure data integrity.

3 Best practices for HMAC

To use HMAC effectively and securely, it's recommended to use a strong hash function, such as SHA-256, SHA-384, or SHA-512. A secure key should be generated randomly, stored securely, and rotated periodically. The key should be long enough to prevent brute-force attacks.

You can't decode it as it's a one way encryption. To validate you need to recreate the the HMAC_SHA256 on your side from the data that has been passed and a shared secret key. You then compare your calculated value to one provided and if they match you know the data hasn't been tampered with.

How to generate HMAC secret key? ›

A message authentication code (MAC) is similar to a cryptographic hash, except that it is based on a secret key. When secret key information is included with the data that is processed by a cryptographic hash function, the resulting hash is known as an HMAC.

Your project must have a service account and have an HMAC key associated with it. The service account must be granted the required permissions to perform actions in Cloud Storage.

HMAC does not encrypt the message. Instead, the message (encrypted or not) must be sent alongside the HMAC hash. Parties with the secret key will hash the message again themselves, and if it is authentic, the received and computed hashes will match.

Hashing is a data security technique used to convert data values into alternate, unique identifiers called hashes for quick and secure access. Hashing can be used for data security because the one-way process prevents access to or tampering with the source data.

HMACMD5 is a type of keyed hash algorithm that is constructed from the Message Digest Algorithm 5 (MD5) hash function and used as a Hash-based Message Authentication Code (HMAC).

HMAC stands for "Hash-based Message Authentication Code," and SHA-256 refers to the Secure Hash Algorithm 256-bit variant. HMAC-SHA-256 combines the strength of SHA-256's cryptographic hashing with HMAC's ability to authenticate the integrity and source of a message.

You can't decode it as it's a one way encryption. To validate you need to recreate the the HMAC_SHA256 on your side from the data that has been passed and a shared secret key.