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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years, 3 months
seen 11 hours ago

11h
comment What can be learned from the ciphertext of LibSodium's crypto_box_detached()?
Three times "no".
14h
comment Format Preserving Encryption for 32 or 64 bit plaintext values
You might be interested in the AEZ Caesar candidate.
1d
comment Smart card minidriver: CryptAcquireContext failed with error 0x80090016 (NTE_BAD_KEYSET)
This is a programming / hardware debugging question. Not a question about cryptography.
2d
comment What is the use of Mersenne Primes in cryptography
Some ECC implementation use extension fields with characteristic $2^{127}-1$. One example is snowshoe.
2d
comment What is the use of Mersenne Primes in cryptography
While we use mersenne primes in crypto, we only use medium sized numbers. So the search for larger (mersenne) primes doesn't have crypto applications.
2d
comment Encrypt a file for random access but only after an initial read of the whole file
@Travis you forgot to salt the password hash.
2d
comment Encrypt a file for random access but only after an initial read of the whole file
@otus It's key dependent processing of the whole file. Since the intention of the OP is to only allow checking if the password is valid after processing the whole file, this should suffice.
2d
comment Is it just as difficult to find a desired output in a hash digest, for MSB vs LSB?
The first byte after the 1 is extremely biased. Character Characters 2 to P occur with about 4.3% probability, characters R to z with 0.07% probability. 1 and Q are somewhere in the middle. I believe this results from the rare characters being impossible if the address has the usual length, only occurring in the rare case where the number is small enough to have a shorter encoding. The bias quickly disappears as you get to less significant digits.
2d
comment Encrypt a file for random access but only after an initial read of the whole file
I wouldn't bother. Just focus on using a good password based KDF (such as scrypt). That way an attacker can verify the file with only a few bytes but they still incur the cost of the KDF for each password.
2d
comment Encrypt a file for random access but only after an initial read of the whole file
@StephenTouset As far as I can tell it does. You first need to commit to a password and then process the whole file to learn the actual key and thus any information about the file.
Oct
21
comment What's algorithm encryption ?Twofish or AES
Even if you're given full access to the encryption function so that you can ask for encryption/decryption of arbitrary plain-/ciphertexts you still won't be able to distinguish AES and Twofish unless you manage to guess the key.
Oct
21
comment Small Prime Difference in RSA
Where is the advantage of this over straight up trial division starting at $\sqrt{n}$?
Oct
21
comment Why do the elliptic curves recommended by NIST use 521 bits rather than 512?
Primes of this form $2^n-1$ are known as Mersenne primes.
Oct
21
comment Small Prime Difference in RSA
1) Compute the square root of the product. 2) Go to the next odd number. 3) Test if division works. 4) If not, add 2 and repeat from step 3.
Oct
20
comment Protection of Elliptic Curve Implementations against side-channel attacks
Some people care about software implementations and talk about the relevant performance and side channels, other people care about hardware implementations and talk about the relevant performance and side channels. The linked talk falls in the software category.
Oct
16
comment How do you test randomness?
Short answer: You can't test if it's good. You can only check if it's bad in specific ways.
Oct
14
comment Can Diffie-Hellman be scaled up or force-multiplied?
@AndrewHoffman That's the case, but I don't get your point. If establishing a connection needs a terabyte RSA key and hours of computation, that's not acceptable performance for me.
Oct
14
comment Can Diffie-Hellman be scaled up or force-multiplied?
When you're worried about quantum computers, don't use RSA or Diffie-Hellman. With these algorithms increasing sizes enough to avoid QCs implies unacceptable performance for the defender.
Oct
13
comment How can convert affine to Jacobian coordinates?
Note that the division in the Jacobian -> Affine transformation is based on the Modular multiplicative inverse. You can't just use the integer division operation offered by common programming languages.
Oct
11
comment Rijndael performance
You implemented it, so you need to benchmark how fast it is. How should we knows? CPUs are too complex to simply deduce performance from the number of operations.