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3

No, there is no known way. It would actually be rather surprising if there were even a theoretical way; the SHA-256 and the SHA-512 compression functions are rather different (for one, one works with 32 bit words and the other works with 64 bit words); one wouldn't expect them to share any sort of relation.


3

First to explain you, why you get 512-bit outputs from a 256-bit curve: The output is basically a point (x-coordinate is enough) and a message-dependant value, with the x-coordinate being expressed as integer. You can verify the signature by checking for a specific relationship between the point and the message-dependant value and the public key point. In ...


0

You really want to authenticate, what use is confidentiality if some random intruder can pretend to be either host or client, or can insert themselves in the middle of the conversation? No need to break the encryption, you'd just give away the keys. If you need to protect the data from being seen, you also need to protect from more active attacks. There ...


2

No. First, you've exposed a padding oracle by using unauthenticated AES. Secondly, you've not authenticated the devices: it's easy to mount a man in the middle attack. Thirdly, I don't understand the role of changing parameters all the time in your protocol.


1

PGP [1024-bit] digital signature vs SHA256 HMAC Comparison... First, you can compare asymmetric and symmetric algorithms. A 1024-bit asymmetric key provides about 80-bits of security. A SHA256 HMAC provides about 128-bits of security. With all other things being equal, the HMAC is stronger. Second, I believe PGP (or is it GnuPG) uses Lim-Lee primes and ...


1

Questions like these are hard to answer because who can predict what the future holds, right? That said, there are some things I wanted to share. Prefer symmetric cryptography over public-key cryptography. Prefer conventional discrete-log-based systems over elliptic-curve systems; the latter have constants that the NSA influences when they can. From NSA ...


7

In computer science, and implementation of crypto, ROTL stands for ROTate Left. ROTL is also noted ROL, or RLNC for Rotate Left No Carry. On a $w$-bit word with bits numbered from $0$, bit number $j$ of the input of ROTL with a shift count of $n$ goes to bit $j+n\bmod w$ of the result; $n=1$ unless otherwise specified (and is the only value available on ...


1

Using AES as a Davies Meyer compression function is a bad idea: It has a block size of 128 bits, which limits its collision resistance to 64 bits, which is rather weak. This limitation could be overcome by using Rijndael with a 256 bit block size, but then you'd need to use a higher number of rounds. AES has been designed to work with randomly chosen ...


0

I looked more into it and saw that the state input is the data input of the block cipher and the data (that is being hashed) is the key input to the underlying block cipher (SHACAL). Thanks anyway.



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