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Jun
29
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Jun
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awarded  Nice Question
Jun
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Jun
13
comment Encryption of exe file
Encryption works on anything, not just "text".
Jun
6
revised SHA-256 hash of null input?
make clear what is wanted
Jun
6
comment Are there security issues with adding plaintext length to TLS packets?
Note that your changed protocol will not be compatible to TLS anymore.
Jun
6
comment Share two secrets between two parties
Welcome to Cryptography Stack Exchange. We actually prefer answers which contain the information itself, not just referring to information elsewhere. Could you add a summary of the information to the answer? Otherwise we will convert your answer to a comment.
May
29
revised Is it practical to use a stream cipher in a block cipher mode?
added 4 characters in body
May
29
revised Is it practical to use a stream cipher in a block cipher mode?
make clear which answer is meant to be wrong (it was the accepted answer when this was written).
May
28
revised Is it practical to use a stream cipher in a block cipher mode?
add disclaimer to the top
May
28
comment Is it practical to use a stream cipher in a block cipher mode?
Actually, my answer didn't say "you can't convert a stream cipher into a block cipher", but "the way of converting which was proposed in the question doesn't work". I'll try to edit it.
May
28
revised Is it practical to use a stream cipher in a block cipher mode?
formatting
May
27
comment Effective security of block cipher – equal the key size, or half the key size?
@Dillinur If I remember right, there is a generic quantum algorithm which finds preimages to functions in $O(\sqrt{N})$ time, where $N$ is the number of possible candidates (i.e. $O(\sqrt{2^n}) = O(2^{n/2})$ for $N = 2^n$). Of course, for this to actually work, you need a quite large quantum computer (about $n$ qbits, I think), and also fast enough. Then it depends on the constant factor to see if it is faster than regular brute-force.
May
27
comment Effective security of block cipher – equal the key size, or half the key size?
Also, this only seems to work with a fixed initialization vector (or if you somehow manage to query the block cipher itself), right? (I guess a "chosen-IV-fixed-known-plaintext" attack on CBC allows this.)
May
27
comment Effective security of block cipher – equal the key size, or half the key size?
Maybe the algorithm would be clearer if the first loop used $X$ instead of $T$ as a variable name? (Also, the hash table access is likely not O(1), but $O(\log(2^{n/2})) = O(n)$. Still almost negligible compared to $O(2^{n/2})$.)
May
26
comment Effective security of block cipher – equal the key size, or half the key size?
@J.D. Please add this as an answer (with some details of how this attack works and a reference to a paper or similar).
May
25
comment Is it practical to use a stream cipher in a block cipher mode?
@J.D. consider adding an answer to the question linked in my previous comment, if that is not already covered by one of the answers there.
May
25
comment Can you make a hash out of a stream cipher?
If you have a PRF, why can't we use that directly as the compression function? It looks like unnecessary overhead to first build a PRP from a PRF, and then use Davies-Meyer to remove the P aspect from it?
May
25
revised Can you make a hash out of a stream cipher?
Fiestel → Feistel