New answers tagged hmac
PGP [1024-bit] digital signature vs SHA256 HMAC Comparison... First, you can compare asymmetric and symmetric algorithms. A 1024-bit asymmetric key provides about 80-bits of security. A SHA256 HMAC provides about 128-bits of security. With all other things being equal, the HMAC is stronger. Second, I believe PGP (or is it GnuPG) uses Lim-Lee primes and ...
Questions like these are hard to answer because who can predict what the future holds, right? That said, there are some things I wanted to share. Prefer symmetric cryptography over public-key cryptography. Prefer conventional discrete-log-based systems over elliptic-curve systems; the latter have constants that the NSA influences when they can. From NSA ...
It is "sent over a secure channel like the AES key". It is "safe to use the same HMAC secret for each subsequent AES encrypted message after the initial connection".
With regards to the algorithm, HMAC-SHA256 is considered very secure. As with most symmetric algorithms it can probably not be proven secure, but that should not worry you overmuch. The most important security consideration with HMAC is to use a time consistent compare when verifying the authentication tag. A 256 bit key could be considered for the simple ...
If the MAC'ing is done right (after the encryption) and if you pad the CBC data correctly there's no security risk. Howver changing to CTR or even better to GCM would be better, as both don't operate on whole blocks and GCM even provides authentication.
First, terms: A MAC is a generic term for a class of cryptographic primitives. It's in the same category as "hash" or "PRNG." HMAC is a particular construction that, combined with a suitable cryptographic hash, gives a secure MAC function (it can also be used to generically refer to any HMAC algorithm, since HMAC is secure with pretty much any standard hash, ...
Some research brought up this paper. The authors state that it's possible to significantly reduce the claimed security so that the security is about the same as collision resistance instead of preimage resistance. The details can be read there and in the references.
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