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Jan
23
comment Number of keys when using symmetric and asymmetric encryption?
I wouldn't count an asymmetric keypair as two keys.
Jan
22
comment How does RSA padding work exactly?
PKCS#1 describes two paddings, v1.5 padding (which is weak) and OAEP padding (which is recommended). Don't try to invent your own padding.
Jan
22
comment Diffie-Hellman on infinite groups
If you are talking about groups like integers, rational or real numbers, they have two problems. First the memory requirement is exponential in the size of the exponent and second the computing logarithms is easy.
Jan
22
awarded  Announcer
Jan
20
comment Practical Attack on RSA
Key size is of little relevant when considering side channel attacks. Some kinds of side channel attacks can be prevented by constant time implementations, for some you need to shield the hardware.
Jan
20
comment Why is EdDSA collision-resilient with SHA-512?
It's important do distinguish between collisions of SHA-512 itself and collisions of SHA-512 mod q.
Jan
19
comment Public key encryption and big files with NaCL
Do you know how big the file is before you encrypt it?
Jan
19
comment Why are some $x$ coordinates unsuitable for an ECDSA generator point?
For an elliptic curve, about half the x values have two associated points, the other half of the x values has none (they correspond to the twist of the curve).
Jan
18
comment Performing HMAC with random key before MAC comparison
I've seen suggestions to use this as constant time comparison by people who're afraid that the compiler will optimize the usual constant time comparison code into variable time code.
Jan
16
comment Pollard's Rho - Restricting the random function to the exponents
You want the cheapest possible function that's still good enough. Exponentiation is expensive.
Jan
16
reviewed No Action Needed Exploration of Blum Micali Security By Seed Size
Jan
16
comment I have a keyword and cipher text but cannot decode it please help!
Don't vandalize your own post.
Jan
16
revised I have a keyword and cipher text but cannot decode it please help!
rolled back to a previous revision
Jan
16
revised I have a keyword and cipher text but cannot decode it please help!
rolled back to a previous revision
Jan
16
comment Help converting sha256 to 32-bit stream
I think this is just a weird formulation for "SHA256 outputs a 32 bytes/256 bits which you should then encode with BASE64".
Jan
16
comment Can AES in CCM or GCM counter mode interoperate with AES in “plain” counter mode (CTR)?
Implementing CTR on top of ECB is probably easier than hacking GCM to become CTR.
Jan
16
comment Is ASCON cipher broken?
It only talks about round reduced versions, so it's not a break.
Jan
15
comment Public key encryption and big files with NaCL
1) Salsa20 is a stream cipher, so nonce reuse behaves like one-time-pad key-reuse. crypto.stackexchange.com/… 2) The Poly1305 MAC is a one-time MAC (wegman-carter), so nonce reuse leaks the MAC key for that nonce.
Jan
15
comment Public key encryption and big files with NaCL
1) Do you use a two part nonce, so you can use a different counter as nonce input for each chunk? Reusing the full nonce is fatal. 2) It's essential to use a special counter/nonce for the chunk containing the hash 3) I'd replace the hash by the file size
Jan
15
reviewed Leave Open Entropy in relation to computer security