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Jun
17
reviewed Close Is HMAC needed for a SHA-3 based MAC?
Jun
17
comment SHA1 collision event probability after n iterations
@otus: yes, I did specify "huge $n$".
Jun
17
comment SHA1 multipart calculation
@GaborForgacs: how is it possible with MD5?
Jun
17
comment SHA1 collision event probability after n iterations
@DmitryKhovratovich: actually, it's not quite correct, however it's in the other direction. It's fairly close for small $n$ (and in this context, $10^9$ is small), however for huge $n$, the cycle structure of iterated SHA1 becomes important. Iterated SHA1 will fall into a cycle eventually, that means that two different inputs have a good probability of falling two different cycles, or two different offsets in the same cycle -- this means that there is a good probability that two different inputs will never collide for any $n$
Jun
16
reviewed Reopen RSA: Common modulus attack problem
Jun
16
comment RSA: Common modulus attack problem
As for what $C_j^{s_i}$ might mean if $s_i < 0$, well, remember that we're doing this modulo $N$. We have $a^{b} a^{c} = a^{b+c}$ for any $a, b, c$, so we have $a^{-b} a^{b} = a^0 = 1$. So, by $a^{-b}$, we mean that value which, when multiplied by $a^b$ (modulo $N$), we get one. And, we can find such values using the Extended Euclidean method. Does that help?
Jun
16
reviewed Edit Why is asymmetric cryptography bad for huge data?
Jun
16
revised Why is asymmetric cryptography bad for huge data?
Add a concept
Jun
15
reviewed Leave Open How to calculate inverse affine transform in AES from forward affine transform?
Jun
15
reviewed No Action Needed How to calculate inverse affine transform in AES from forward affine transform?
Jun
13
reviewed Leave Open RSA decrypting of a huge file by parts
Jun
13
reviewed Close Algorithm accepting every passphrase to fool unlegit user
Jun
12
answered Brute force RSA cracking
Jun
11
comment Why must IV be sent with each packet?
Yes, I meant CBC mode specifically -- somehow that didn't make it into the comment...
Jun
11
comment Why must IV be sent with each packet?
Depending on the mode that uses the IV, this may not be great advice. For example, using a counter as an IV (even if some of the counter bits are hidden) might not be a great idea if the initial plaintext blocks of adjacent packets have a good probability in differing only in their LSBits.
Jun
11
reviewed Edit Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?
Jun
11
revised Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?
improved formatting -- I rejected replacing "xor" with $\oplus$ -- IMHO, xor is actually clearer
Jun
11
reviewed Leave Open Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?
Jun
11
reviewed No Action Needed Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?
Jun
10
reviewed No Action Needed Generate a unique 64 bit numeric database key from a string without collisions at $2^{32}$ birthday threshold?