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Dec
17
comment Dancing confusion with Daniel J. Bernstein's stream ciphers
a larger nonce does not improve security, it just allows more messages to be processed under the same key
Dec
16
comment How do we find the subkey out of a differential cryptanalysis?
so, like 4 round AES?
Dec
15
comment How to customize a standard encryption algorithm?
summary: methods to improve the diffusion of AES variants that still allow use of AES_NI instructions. new pdf: wikisend.com/download/495024
Dec
15
comment How to customize a standard encryption algorithm?
Note the PDF link is no longer relevant: groups.google.com/forum/#!topic/sci.crypt/G59kkTswyjk
Dec
13
comment Bae64 with shuffled alphabet
If you decode from 6 to 8 bit raw values, you may be able to perform a frequency analysis. This would require the entire 64 character alphabet to be known, and for you to assign arbitrary values to them.
Dec
13
comment Bae64 with shuffled alphabet
There are several published base64 variations, try those first. I even have my own variant (url/filename safe, no padding). The value used for < may indicate if a known variant is used
Dec
13
answered Why do we have fixed output length in the algorithm SHA1
Dec
9
comment Are there any proofs of the SHA1 compression function's (second-)preimage resistance?
the generalizations on key recovery from block ciphers using differential or linear analysis is what you should be looking at, since the message is treated as the key to a block cipher in SHA
Dec
7
comment Memory-expensive hash from an array of hashes?
I would suggest that you make the array size at least 4X the size of the total largest L2 cache on whatever device you are trying to defend against (including in the future), which is currently 2MB (Maxwell), so a 16-32MB minimum array
Dec
7
comment Memory-expensive hash from an array of hashes?
scrypt has some issues, and has a complex implementation, there is great demand for alternatives. I use this exact method with 16 round SHA-256 in an experimental password hashing scheme, it has provable properties, but bad implementation can lead to information leakage
Dec
5
comment SHA1 Collisions - what about practical attacks?
I think you may have misread his question, he is concerned about malicious collisions in a cryptographic hash function, which will allow forgery of a digital signature.
Dec
4
comment Timestamp assignment and meaning
I would assume it is the system time expressed as an integer, possibly exponentiated with the private key, or just appended to the message? do you have additional context?
Dec
4
answered Arithmetic modulo 1
Dec
4
comment Are modified implementations of cryptographic algorithms a good idea?
They put the results of the Davies attack paper into a revised version of their earlier paper, cs.technion.ac.il/users/wwwb/cgi-bin/tr-info.cgi?1994/CS/CS0816
Dec
4
comment Retrieve timestamp from TOTP value
if you have the key, you can generate the value for all time codes +- a few hours and compare, it should only take a few seconds. Also, you should be using UTC time in order to avoid time zone issues
Dec
4
comment Arithmetic modulo 1
I think the value is supposed to be fractional, and in that case mod 1 results in a value between 0 and < 1
Dec
4
comment What approach is used here?
is it possible it is encoded in trinary?
Dec
3
comment Are modified implementations of cryptographic algorithms a good idea?
it is behind paywalls, but it was from Eurocrypt 94, "An Improvement of Davies’ Attack on DES", by Eli Biham and Alex Biryukov
Dec
3
comment I don't care about replay attacks. What should I do with the nonce in nacl?
in this case they would not need to, and if you fix it it would not be sent, but generally the nonce is sent along with the ciphertext, so the attacker knows it anyway
Dec
3
comment I don't care about replay attacks. What should I do with the nonce in nacl?
whatever plainext is known or chosen, a nonce reuse will expose any message up to that length. I assume we are talking about a block cipher in CTR mode here