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Sep
8
comment Find pixel mapping matrix with minimum iterations
@AnthonyKeane: this isn't a C writing service. I would suggest instead that you think about the problem; if you were given a 2x2 array, how can you do it with 2 queries? Then, if you were given a 4x4 array, how can you do it with 4 queries? If you can answer those two questions, generalizing it to nxn arrays should be easy.
Sep
6
reviewed Leave Closed Find pixel mapping matrix with minimum iterations
Sep
6
comment Find pixel mapping matrix with minimum iterations
@AnthonyKeane: 24 queries
Sep
6
comment Find pixel mapping matrix with minimum iterations
The answer to the question is "yes, there is such an algorithm". Hint: given the above example, you can do it with 6 queries.
Sep
5
answered Base64 for a hash algorithm
Sep
5
reviewed Leave Open Can Bitcoin HD public keys be used for symmetric encryption?
Sep
5
reviewed Close Find pixel mapping matrix with minimum iterations
Sep
4
reviewed Close Higher residuosity problem, but with a known factorization
Sep
4
comment Would xoring 2 independant AES CTRs to produce p-rand introduce vulnerabilities?
@John: no, there are cleverer ways to recover the initial state. However, if you use AES-256, any such method would have to start out with "try to find a 256 key which...", which is completely infeasible. Of course, is there a specific reason why you just don't do simple counter mode with a single AES-256 key?
Sep
4
reviewed Approve suggested edit on ECIES: Purpose of MAC?
Sep
4
answered Would xoring 2 independant AES CTRs to produce p-rand introduce vulnerabilities?
Sep
4
reviewed Close Cracking WWII-era codes - code found on a pigeon's leg in Surrey
Sep
4
comment ECIES: Purpose of MAC?
@tryagain: However, should could not compose "Transfer one million into Eve's account, password Rhinosaurus" if she doesn't know the password. That's the point of the example; by modifying the message, she doesn't have to know it.
Sep
4
comment ECIES: Purpose of MAC?
@tryagain: look at the example I gave above; it is actually secure. Eve could not generate the message, because she doesn't know the password. Or, are you saying that ECIES should have been designed with a known weakness (message malleability) because that weakness is likely to be covered by how it is used?
Sep
4
answered ECIES: Purpose of MAC?
Sep
3
comment What are options to compute DES retail MAC (aka ISO 9797-1 mode 3) under PKCS#11?
Are you intending to use this in a real product? There's an obvious key recovery attack with $2^{32}$ known plaintext/MACs and $2^{57}$ work; that's too close to practical for me...
Sep
3
comment Encryption-Decryption-Encryption
@CodesInChaos: hey, if I hadn't bothered typing in all of "This isn't a quite a duplicate...", I would have been first :-)
Sep
3
comment Encryption-Decryption-Encryption
This isn't quite a duplicate, however a related question (specific to DES) is crypto.stackexchange.com/questions/2060/…
Sep
3
reviewed Close What is the exact purpose of length padding in Merkle–Damgård hash functions?
Sep
2
reviewed Close How Proof all Subgroup point of prime order elliptic curve have prime order [#G=#E]?