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 Oct 9 comment Construct points with the same discrete logarithm I assume a multiparty computation (where no one side knows the discrete log) is out of the question? Oct 9 answered Inverting RSA function Oct 9 awarded collision-resistance Oct 8 reviewed Looks OK How to find the value of a vector modulo a basis in lattice-based cryptography Oct 8 answered How does perfect hash function works? Oct 8 comment Is it worth hiding an AES encrypted text string in a PNG image for better security? What aspect of security are you talking about? Are you concerned about someone decrypting the encrypted string? Or, are you concerned that someone would detect that there was an encrypted string there? Oct 7 answered Security of SRP-6a against impersonating server choosing small/wrong N Oct 6 comment Calculating the average key search time of DES @TalenKylon: well, the most significant bits contribute to the key value (it's the lsbits that are ignored), and so that would reduce the key space to 48 bits. Also, when someone says "ASCII character", they often mean "printable ASCII character", that is, a value between 0x20 and 0x7e; that would reduce the keyspace somewhat more. Oct 5 answered Calculating the average key search time of DES Oct 5 comment Is it possible to apply hill-climbing algorithm to Diffie–Hellman? Actually, it's quite easy to give them a metric with the actual solution as a local maximum. What's difficult is to give a metric that gives a useful indication of "you're close" Oct 5 comment RSA 1024 bit forge a new matching signature from a chosen message Attempting to recover $d$ is a deadend. Instead, you should attempt to figure out how to deduce a signature without knowing $d$. Hint: the relation $a^d \times b^d = (ab)^d \pmod N$ is useful. Oct 5 comment RSA 1024 bit forge a new matching signature from a chosen message There is no known way to recover $d = 3^{-1} \bmod lcm(P-1, Q-1)$ given access to an oracle that computes $f(x) = x^d \bmod N$. Are you sure that your teacher didn't ask you to compute the signature for another message that you haven't been given the signature to? Oct 5 comment Byte size of Diffie-Hellman public values @thotheolh: the obvious way to represent A and B are in arrays of 256 bytes. Oct 5 answered Byte size of Diffie-Hellman public values Oct 4 answered How is RSA able to prevent brute forcing using the public key? Oct 3 comment Why not to use curve over field of $p^m$ with $p > 2$ for ECDSA? "Arithmetic gets more involved for $GF(p^m), m>1$..."; actually, the fastest known curve with circa 128 bit security is FourQ; it has $m=2$ (and $p= 2^{127}-1$) Oct 2 awarded Necromancer Oct 1 comment Combining md5 collisions to create more collisions Short answer: yes. As for how, see: iacr.org/archive/crypto2004/31520306/multicollisions.pdf . With this technique, a billion-way collision is quite feasible. Oct 1 revised Encrypting a 160-bit plaintext into a 160 bit ciphertext with a 128-bit Block Cipher edited tags Oct 1 comment Is it possible to add error propagation to OTP? @RichieFrame: nit, $GF(2^{8})$ multiplication wouldn't work, as a 0 in the pad would kill things. However, $GF(257)$ multiplication (with the convention that the 0x00 byte stands for the value 256) would work.