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20h
comment Is Shamir's Secret Sharing Scheme insecure for larger field?
when that is the case it is like you are not using the mod p at all, an attacker can skip that step completely, substantially reducing the effort to guess values if points are known
21h
comment Is Shamir's Secret Sharing Scheme insecure for larger field?
what that means is f(x) is smaller than p, so mod p does not change the value
1d
comment How does hash speed vary based on string length?
with PBKDF2-SHA256, an extra hash iteration due to a very long input is inconsequential when you have an iteration count of a quarter million
1d
comment Diffie-Hellman key size to symmetric formula?
should not the 256-bit security be 15360-bit RSA, and 128-bit security be 3072-bit RSA, etc? I have not seen the values in your question with the given security levels
2d
answered Possible to generate a one time secret which all nodes on the distributed network can know but cannot pre compute
2d
comment Are these hash function compositions collision resistant?
@naervaer no, it is still collision resistant if $H$ is, however the expected collision resistance does not increase, even though the size of the output doubles, which is what one expects when the hash output increases.
2d
answered Are these hash function compositions collision resistant?
2d
reviewed Approve Are these hash function compositions collision resistant?
Feb
10
comment Security of a parallelizable block cipher mode
now you have XE mode with a highly nonlinear delta at the expense of an additional encrypt operation per block, it would be best to use it like CT = E_K(PT xor BT) xor BT, which is an XEX mode, and would be more secure against adaptive chosen ciphertext attacks.
Feb
9
comment What are the pre-requisites I need to be able to code Salsa20 in C#?
if you can code DES, you can code Salsa, since it has a much more simple description and is designed for ease of software implementation
Feb
5
answered Deriving a key for HMAC, using PBKDF2
Feb
5
answered NIST HMAC Test vectors
Feb
5
comment OCB(Offset Code Book) authentication encryption
I was able to implement OCB correctly based solely on the RFC, it is thorough enough
Feb
4
comment Classification of a stream cipher
@alpha_numeric an example of non-additive would be a byte of keystream used to choose one of 256 s-boxes, and the plaintext is then run through the s-box
Feb
4
comment Classification of a stream cipher
@alpha_numeric a sponge construction is just one way to build a cipher that way, specifically using a duplex type mode similar to MonkeyDuplex. there are other constructions that will also fit. Also there are many sponge based ciphers, the CEASAR competition has about a dozen, see NORX, and I am developing my own for fun. They also do not give a more generalized description of the ciphers, since they are all authenticated.
Feb
4
comment Security of a parallelizable block cipher mode
@IlmariKaronen that is used in the SHA documentation for modular addition
Feb
4
comment Security of a parallelizable block cipher mode
what happens if you blocks with values that increment sequentially?
Feb
3
answered Classification of a stream cipher
Feb
2
comment Classification of a stream cipher
Actually there are several ciphers that work similar in practice, except that they depend on blocks of prior bytes, rather than individual prior bytes. See NORX for example
Feb
1
comment Can an AES-256 key be generated for a large number of cribs?
don't those things use a random AES key for each file, then encrypt that random key with an RSA key?