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HMAC is a method for constructing a message authentication code based on a cryptographic hash function.

0 votes

Key derivation using the main AES encryption key and some plain text?

It would be better to use your main key to derive two separate keys, one for encryption, and one for HMAC... and using the info parameter to distinguish the two keys. …
hunter's user avatar
  • 4,007
3 votes

SHA3 HMAC key padding

In lieu of any answers; I've compared my own implementation with the few test vectors I've been able to find (one of which can be found here) and it would appear that yes, keys longer than the block-s …
hunter's user avatar
  • 4,007
4 votes

Encryption and HMAC key derivation

If you go with Scrypt (which I would recommend you do), there are no restrictions on the size of the passphrase... and Scrypt consumes it internally with one round of PBKDF2-HMAC-SHA256 anyway. … When generating the HMAC authentication and encryption keys, would I benefit at all from using SHA-512? No, you wouldn't. In fact, this step is unnecessary. …
hunter's user avatar
  • 4,007
10 votes
Accepted

How to use HMAC-SHA1, HMAC-SHA2 in conjunction with AES

Using a HMAC provides this integrity. … A HMAC solves this problem as it uses a key - meaning that an attacker is unable to create a valid HMAC unless they have a valid key (which only you possess). …
Dmitry Khovratovich's user avatar
5 votes

Using one-way hash functions as the encryption method

"Frequency analysis of the output might help determine simple words in the ciphertext such as 'the' etc if that word is repeated and sent multiple times. This isn't necessarily a problem as it' …
hunter's user avatar
  • 4,007
1 vote

RSA digital signature vs authenticated cipher

Your options should really be either using GCM mode, or using a non-authenticated mode (such as CBC) and calculating the HMAC (with something like HMAC-SHA256) post-encryption. … The second option, encrypt-then-hmac, is fine too, but there's more room for error. …
hunter's user avatar
  • 4,007
29 votes

What is the difference between a HMAC and a hash of data?

With a HMAC, a key is used when calculating the hash value, so unless the attacker has the key, they're unable to calculate a valid hash value of the modified data. …
hunter's user avatar
  • 4,007