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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years, 6 months
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Jan
4
reviewed Leave Open Why are there no MACs inspired by block cipher modes other than CBC and CFB?
Jan
3
reviewed Close can anyone give the java code to encrypt files using paillier
Jan
3
reviewed Close How will Cryptography be changed by Quantum Computing?
Jan
3
revised C# implementation of curve25519 to ed25519 conversions
added 153 characters in body
Jan
3
revised C# implementation of curve25519 to ed25519 conversions
added 119 characters in body
Jan
3
comment Is BBS used for generation of keys for any modem cryptosystem?
Why do you ask?
Jan
3
answered C# implementation of curve25519 to ed25519 conversions
Jan
3
comment RSA - Why should we sign hash rather than raw content?
The size limitation is similar for encryption and signing. It's the size of the modulus (256 bytes for RSA 2028) minus some space reserved for of padding (40ish bytes). The reason you never heard "we can't encrypt a file bigger than 256 bytes using a RSA public key" is because nobody (competent) does that. RSA encryption is almost always hybrid encryption i.e. you only encrypt a random key with RSA and the rest with symmetric encryption like AES. Just li
Jan
2
comment (Re-)Using deterministic IV in CTR mode / How to: deterministic AES
Since you'll need to publish the IV, it's essential that the derivation function is keyed.
Jan
2
comment Are there cryptographic hash functions which do not have any collisions?
There exist one-way functions which have no collisions, but obviously their output will be at least the size of the input.
Jan
2
comment (Re-)Using deterministic IV in CTR mode / How to: deterministic AES
Search for BEAR, LION, LIONESS. Might be relevant
Jan
2
comment Size of a MAC for a quickly checked message?
I'd use between 8 and 16 bytes, depending on the desired security level.
Dec
29
comment How to use NaCl with Java under Windows
This question appears to be off-topic because it is about programming.
Dec
28
comment Can I simulate iterated AES-ECB with other block cipher modes?
Has been some time since I looked at keepass2, but from what I remember it was equivalent to two independent uses of CBC with zero bytes as data.
Dec
26
comment How to verify the result of repeated squaring method
you can check if $(x^d)^e=x \pmod n$, which takes few steps if $e$ is small (as is typical for RSA)
Dec
26
comment Which Block cipher mode should I use?
The best choice of block cipher mode depends on context. Apart from ECB all popular modes are semantically secure. But perhaps you need integrity checks, in which case you might want authenticated encryption, like AES-GCM or a traditional MAC in an encrypt-then-mac scheme. Sometimes you need to preserve the length, sometimes you need nonce reuse resistance, sometimes you need asymmetric authentication, sometimes you worry about certain side-channels, sometimes you don't...
Dec
25
comment test vectors for 3DES seem to in fact be testing DES - not 3DES
Did you confuse bits and bytes? DES has a 56/64 bit key and 3DES has a 168/192 bit key.
Dec
25
answered Security concern about reducing hash value using modulo operation
Dec
25
awarded  encryption
Dec
24
comment Do Brute-Force Attacks and Cryptanalysis refute Kerckhoffs's principle?
@xorcoder The limits of brute-force are much lower. Even for 400 bit keys it's quite optimistic. You're underestimating the exponential function.