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5h
revised Generation of N bit prime numbers -> what is the actual range?
added 33 characters in body
5h
answered Generation of N bit prime numbers -> what is the actual range?
5h
comment Using modulus in one time pad?
@GuutBoy: actually, the group doesn't need to be cyclic; given $d$ and $C$, that there is a unique $k$ s.t. $C=d+k$ is a property of all groups, cyclic or not. As for why the group needs to be finite, well, for groups of size $\aleph_0$, you can't select a random element equiprobably, and for groups of size $\aleph_1$ and larger, well, you run into issues that you can't express almost all the members within a finite number of bits.
10h
comment Using modulus in one time pad?
@zof: it is there in order to make the +/- an operation over a finite group; OTP needs to be performed over a finite group (or, at least, a finite latin square) in order to be secure.
11h
revised AES Affine Transformation in $GF(2^4)$
added 1 character in body
11h
revised AES Affine Transformation in $GF(2^4)$
edited body
12h
revised AES Affine Transformation in $GF(2^4)$
edited body
12h
comment AES Affine Transformation in $GF(2^4)$
I tried to answer your question; however might I inquire why you're asking? What problem are you trying to solve.
12h
answered AES Affine Transformation in $GF(2^4)$
2d
comment Diffie-Hellman and man-in-the-middle attacks
@GuutBoy: $g^a$ and $g^b$ are 'public keys' in the sense that they allow you to compute some of the operations on the key, but not all. It's clearer when you consider long term DH. As for the corresponding private key, that's $a$ and $b$
Sep
19
comment Diffie-Hellman and man-in-the-middle attacks
@GuutBoy: actually, while we don't typically call the values $g^a$ and $g^b$ exchanged in the DH key exchange "public keys", it doesn't do violence to the language to call them that, and in fact they are on occasion referred to as public keys. They do share the attributes that we normally expect from "public keys".
Sep
19
comment Is it possible (how difficult) to find MORE than one valid RSA signature?
@CodesInChaos: actually, if $\operatorname{GCD}(e, \phi(n)) > 1$, then it's more likely that no such signature exists. However, if one does exist, it is likely that many others do as well (if $e$ is prime, both $e$ and $e^2$ total are possible).
Sep
19
comment Is it possible (how difficult) to find MORE than one valid RSA signature?
Depends entirely on the padding method. With any nondetermanistic padding method (e.g. PSS), it's easy. With, say, PKCS#1.5, well, I suppose you could generate distinct signatures by using different hash functions (say, SHA-256 and SHA-512)
Sep
18
comment GCM: Math behind update of AAD after ciphertext has been processed
@owlstead: that'd work too... That's more work to handle the A||C||A case, however if you're optimizing for the A||C case (and just want to handle the A||C||A case correctly, and not dreadfully slowly), that's a reasonable solution.
Sep
18
answered Is there any definition for “generic attack” in context of cryptography or more specific “hash functions”?
Sep
18
reviewed Leave Closed Is appending the hash of the plaintext to the end of an encrypted message sufficient to ensure integrity?
Sep
18
reviewed No Action Needed How do institutions like banks do RSA with big primes?
Sep
18
reviewed No Action Needed VKO GOST R 34.10-2001 (described in RFC4357), Key Agreement Algorithm. Looking for its implementation/detailed description/examples
Sep
18
comment GCM: Math behind update of AAD after ciphertext has been processed
@owlstead: I don't believe that quite works (unless you know the length of the AAD beforehand). The problem is that if you've already computed $\operatorname{GHASH}_H(A_{0..x}||C)$, there's no easy way to insert $A_{(x+1)...z}$ into the middle. If that's a requirement, I would suggest you keep running $\operatorname{GHASH}_H(A_{0..x})$ and $\operatorname{GHASH}_H(C_{0..y})$, and glue them together only when you've seen the entire $A$
Sep
17
reviewed No Action Needed Finding algorithm: desire RSA's uniqueness and ECDSA's space efficiency