Contents
How is the secret key used in HMAC?
For example, suppose Alice keeps her secret key to herself and only ever uses it to compute MACs of messages that she stores on a cloud server or other unreliable storage media. If she later reads back a message and sees a correct MAC attached to it, she knows that this is one of the messages that she stored in the past.
Which is an example of HMAC in a Mac?
For example, suppose that Alice stores successive versions of multiple files on an unreliable media, together with their MACs. (Again we assume that only Alice knows the secret key.)
Is the photograph the key to the HMAC?
Your key is the HMAC’s key. The photograph is the data you are applying the HMAC to. The above is a round trip metaphor where only you have a key. In a different situation, let’s say you often send packages to Tommy. You’re worried that the nosey mail carriers might be opening your packages and replacing the photographs or changing them.
Are there any downsides to using HMAC?
HMAC relies on symmetric key cryptography and pre-shared secrets instead of private/public pairs. The downside is the same as with symmetric key cryptography in general – you now need to worry about distribution and protection of your secret keys.
The secret key is first used to derive two keys – inner and outer. The first pass of the algorithm produces an internal hash derived from the message and the inner key. The second pass produces the final HMAC code derived from the inner hash result and the outer key.
What’s the difference between salted hash and keyed hashing?
A cryptographic salt is additional input other than message itself for a hash function so that it prevents attacker from launching dictionary attacks. Usually the salt is stored along with the hash of say the password etc. Keyed Hashing is secret key is used as input for hashing along with message like HMAC.
How is keyed hashing used in message authentication?
Keyed hashing is usually used to build message authentication codes (MACs), the most common of which is the hashed-based MAC (HMAC).
What kind of hash function is used for HMAC?
Any cryptographic hash function, such as SHA-2 or SHA-3, may be used in the calculation of an HMAC; the resulting MAC algorithm is termed HMAC-X, where X is the hash function used (e.g. HMAC-SHA256 or HMAC-SHA3-512).
What does HMAC stand for In cryptography category?
HMAC can provide message authentication using a shared secret instead of using digital signatures with asymmetric cryptography.
Do you have to encrypt the message with HMAC?
HMAC does not encrypt the message. Instead, the message (encrypted or not) must be sent alongside the HMAC hash.