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Jun
2
answered Use additional keys to thwart key compromise?
Jun
2
comment Which one of the Block Cipher modes is the best?
There is no "best". Best for what purpose? They have different characteristics. Those characteristics are well-documented.
Jun
2
answered Encryption of log files
Jun
2
comment Security of a security protocol for key exchange, using symmetric-key cryptography
Have you tried using an automated protocol analyzer, like AVISPA, ProVerif, CryptoVerif, Scyther, Tamarin, EasyCrypt, CertiCrypt, Maude-NPA, etc.?
Jun
2
revised Reductionist proofs of decisional problems to computational
added 217 characters in body
Jun
2
answered Update to “Cryptographic Right Answers”
Jun
2
comment Why is plain-hash-then-encrypt not a secure MAC?
@IlmariKaronen, Good point! This is worth considering and discussing. Looks like there are many possibilities. Another possibility that might make even more sense would be to close this question as a dup of crypto.stackexchange.com/q/6069/351, since they are both specifically about stream ciphers. (I do not suggest closing Gilles' older question as a dup of this one; I think Gilles' older question is better-written and better-researched, whereas I find this question a bit confusing and hard to follow.)
Jun
2
answered Reductionist proofs of decisional problems to computational
Jun
1
awarded  Notable Question
May
31
comment Security of the iterated Hill Cipher
@LinearAlgebra, OK, I've edited my answer to show how to break the revised scheme, given your updated question.
May
31
revised Security of the iterated Hill Cipher
added 2042 characters in body
May
31
revised Creating a license system based on asymmetric encryption (RSA or ECDSA)
added 14 characters in body; added 1420 characters in body
May
31
comment Creating a license system based on asymmetric encryption (RSA or ECDSA)
@CodeX, sure. I expanded my answer to elaborate further on revocation (your question #3) and stolen private keys (your question #4).
May
31
revised Creating a license system based on asymmetric encryption (RSA or ECDSA)
added 14 characters in body; added 1420 characters in body
May
31
comment Why is plain-hash-then-encrypt not a secure MAC?
@e-sushi, this question asks whether $\text{Encrypt}(M || H(m))$ is secure, where $H$ is a hash (not a MAC). The question I linked to asks whether $E_k(M || H(M))$ is secure. It's the same question. OK, the latter question focuses on CBC encryption, but the answers there show an attack when $\text{Encrypt}$ is CBC mode encryption, which already answers this question and shows that this question's scheme is not secure in general. And the case of stream ciphers is already handled by crypto.stackexchange.com/q/6069/351. So this question is completely subsumed by existing questions.
May
31
comment Why is plain-hash-then-encrypt not a secure MAC?
possible duplicate of Does CBC encryption of a hash provide authenticity?
May
31
comment The improvement of the private key exponent in the M.Weiner Attack
I'd expect you to do more research on your own before asking here (on this site we expect you to do a significant amount of research before asking). In the future, one way to answer this sort of thing on your own is to do a literature search.
May
31
revised Security of the iterated Hill Cipher
Improve the title.
May
31
answered Security of the iterated Hill Cipher
May
31
answered Creating a license system based on asymmetric encryption (RSA or ECDSA)