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comment Implementing CD serial key system
100-bits is about 17 characters in base64. A Microsoft style (base32) format key with 5x5 characters gives 125 bits, extending that to 6x5 gives 150-bits (Symantec style). A reformatted base32 key is also more resilient to incorrect keys, since you can treat "O" and "0" as the same value, etc. You may want to separate the "product code" and "license key" to gain more bits for the sig.
Jul
25
answered Does 3-DES take approximately the same time to encrypt 1B and 1KB?
Jul
24
revised Different padding rules for Merkle-Damgard and Keccak/sponge function
Added example collision
Jul
24
comment Different padding rules for Merkle-Damgard and Keccak/sponge function
@CGFoX I will edit my answer with an example
Jul
23
answered Different padding rules for Merkle-Damgard and Keccak/sponge function
Jul
22
comment How can I solve this modular equation?
For a small modulus (13), add it to the result (2) until you get a result divisible by 5 (15), then divide it = 3
Jul
21
comment How do we operate IV+1?
NIST standard is to increment the block counter of the IV mod 2^len_in_bits(counter), so a 32-bit counter would be added mod $2^{32}$. You should not increment the complete IV unless you are keeping track of the nonce bits and make sure they do not increment
Jul
21
comment Choice of multiplication polynomial in Rijndael s-box affine mapping
@poncho No I do not. They concern differential properties, better performance in these tests generally means more resistance to differential cryptanalysis. The AES s-box is already very good in these respects, what I am saying there is that their choice of affine polynomial was not chosen from a subset of those with statistically better properties, so that is not a potential reason not to use a more simple polynomial.
Jul
21
revised Choice of multiplication polynomial in Rijndael s-box affine mapping
Fixed inverse polynomial and updated with statistics
Jul
21
comment Is there a generic attack on encrypted CRC32 when used as a MAC?
CRC is not a MAC at all, it provides no authentication
Jul
19
comment Importance of salt when deriving an encryption key
the brute force attack is against the password, not the key. The purpose of the salt is so the key is not the same if the password is the same. Password recovery on one can allow key recovery of the other.
Jul
19
answered Polynomial representation of the affine part of the AES S-box
Jul
19
comment Polynomial representation of the affine part of the AES S-box
I am misreading things it seems, i read that interpolation as relating to the inversion, which it is not, what the equation is missing is indeed the non-linear step
Jul
19
comment Polynomial representation of the affine part of the AES S-box
they are completely missing that in the equation, which is why the op's code which is based on it is not working
Jul
18
comment Polynomial representation of the affine part of the AES S-box
also missing modulus of polynomial ring, which is different for inversion and affine transform, meaning you need 2 rings
Jul
16
revised Decryption issue with self-coded AES-128
clarity on key schedule
Jul
16
comment Collecting entropy: can I use timing of reading as a separate source from the reading itself?
I would only use the timestamps as part of a healthcheck to make sure you do not get a stream of 0000.. from an input of 010101..., or to detect when there is a continuous 1 or 0 input
Jul
15
comment Decryption issue with self-coded AES-128
Actually that value is just the round number that subkey is applied to, so a decimal or hex representation is equivalent, as long as the round number matches
Jul
15
comment Ciphertext indistinguishability (IND-CPA) for symmetric cryptography
correlation coefficient on the true/false table of guesses be the best way to validate?
Jul
15
answered Decryption issue with self-coded AES-128