(or message authentication code), a short piece of information used to authenticate a message, and the algorithm to create and check such information, using a secret key.

learn more… | top users | synonyms

4
votes
1answer
365 views

GCM vs CTR+HMAC tradeoffs

So these days I see everyone using AES-GCM. What are its advantages over simple CTR+HMAC modes? Is it speed? Or ciphertext length? And what are the security tradeoffs, both in terms of practical ...
1
vote
1answer
90 views

Prove that two MACs with incremendal PRF application are not secure

How do I prove the following MACs are insecure?                                                        1                                                                                   2
1
vote
1answer
169 views

Derive both MAC and AES keys from same PBKDF2?

When doing password-based encryption, is it OK to create one instance of PBKDF2 from the password, and then use it to create both the AES key and the MAC key? (Or should a new instance of PBKDF2 be ...
1
vote
1answer
84 views

Is OCB with short MAC malleable?

At the beginning of OCB's white paper [pdf], OCB is compared to other modes, and non-malleability is one of the properties advertised. At the end of the paper, it is mentioned the MAC length can be ...
11
votes
2answers
328 views

Can I use HMAC-SHA1 in counter mode to make a stream cipher?

Say I have an embedded device which is only capable of doing HMAC-SHA1 transformations (that device is, in fact, a YubiKey). Would it be secure to feed it like a block cipher in counter mode to get a ...
6
votes
2answers
166 views

Does there exist a proof-of-retrievability scheme that is publicly-verifiable, limited-use, and does not use homomorphic encryption?

I find myself wanting to test out a practical implementation of a proof-of-retrievability scheme, simply out of curiosity. These schemes seem to be divided into two variations, publicly-verified and ...