4,332 reputation
731
bio website
location Netherlands
age 40
visits member for 2 years, 9 months
seen 1 hour ago

Java and security expert with over 10 years of experience with the language and with the practical application of cryptographic protocols - including the design of protocols within international standardization bodies. Creator of a heavily used common criteria certified product. Over 30 years of experience with computers. Likes kids, cats, reading, movies and several sports.


Sep
3
revised Entropy of the key
cleared things up according to comments
Sep
3
comment Advantages of using intermediate hash over full hash in digital signature application
Personally I really dislike partial hashes; I'll ask the creators of the protocol as well if they can give substantial reasons to apply them.
Sep
3
asked Advantages of using intermediate hash over full hash in digital signature application
Sep
3
reviewed Close How Proof all Subgroup point of prime order elliptic curve have prime order [#G=#E]?
Sep
2
answered How is the following different than RSA Signing of a document?
Sep
2
revised How is the following different than RSA Signing of a document?
added 1 character in body
Sep
2
comment CBC-MAC based on PRF
OK, maybe "most of the time" is taking it a bit far. The fact that you can use the same primitive as for confidentiality certainly is a feature though. Note that you could of course also use a stream cipher and a derived HMAC for confidentiality. See for instance the Spritz paper.
Sep
1
comment CBC-MAC based on PRF
Did a bit of research, but this algorithm goes back to FIPS 113 (1985), and that "standard" does not do too much reasoning. OMAC and CMAC papers don't list the reason either. So the best answer may be that it uses a PRP because if it was a PRF, it would be a HMAC :P
Sep
1
comment CBC-MAC based on PRF
Why not? Most of the time a PRP is faster, and it is nice if you can use the same primitive for both confidentiality and integrity/authenticity (e.g. CCM & EAX mode of encryption).
Sep
1
comment Are partial hashes used in cryptographic protocols?
@tylo Well, for security tokens/smart cards there is PIN or biometric authentication. That's some kind of "user consent". I agree that there is still plenty that can be done by a malicious terminal though; that's actually one of my peeves against this kind of security - at some point in time you need to trust the terminal anyway. I mean, if a covert channel is possible, then it is also possible to sign any other content, which is much worse.
Sep
1
comment Are partial hashes used in cryptographic protocols?
@tylo Agreed. And it would be rather easy to couple data or meaning to a hash as well. I think you need to be able to trust the data you are signing. The question is then if the partial hash is adding security or not. Of course, a covert channel in signed data is of more importance than a covert channel elsewhere (as there is user consent to create the signature, possibly at a specific time/place).
Aug
31
revised Are partial hashes used in cryptographic protocols?
made the question as little opinion based as possible
Aug
31
asked Are partial hashes used in cryptographic protocols?
Aug
30
comment How should I treat a new cipher release like Spritz?
Added some Spritz related information; interesting cipher indeed. Drop in replacement for RC4 and it resembles a sponge.
Aug
30
revised How should I treat a new cipher release like Spritz?
added 141 characters in body
Aug
30
reviewed Close Good challenges for a crypto competition for teenagers
Aug
30
reviewed Close Security of very simple XOR with random?
Aug
30
reviewed Close Seemingly simple decryption question
Aug
30
reviewed Close What's the best packet cipher mode for use with UDP for example? Advantages or disadvantages of any alternatives?
Aug
30
reviewed Looks OK What is the most secure hand cipher?