9,586 reputation
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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years, 1 month
seen 1 hour ago

Oct
21
reviewed Edit suggested edit on understanding pairing $e:G \times G \to G_T$ and ( Decision)BDH assumption
Oct
21
revised understanding pairing $e:G \times G \to G_T$ and ( Decision)BDH assumption
corrected spelling
Oct
21
comment Security considerations on “expand 32-byte k”-magic number in the Salsa20 famility of stream ciphers?
Choosing all four 32-bit words of the constant as equal is probably a bad idea.
Oct
21
comment Can Secp 256 K1 curves “map” to a value on FIPS 186-3 or P-256?
Conversion works only if the curves are equivalent, but Secp256K1 and P256 are not equivalent.
Oct
18
comment How exactly was the finalist chosen in the NIST AES competition?
Rijndael is actually pretty tricky to implement in software if you want to completely avoid timing side-channels without specialized instructions.
Oct
17
comment Cryptanalysis not based on method used to encrypt?
what do you mean by matrix based cryptography?
Oct
16
comment Can we decrypt in this order when the message is encrypted twice?
It's important to note that xor isn't secure if the attacker can observe the intermediate values $E_{k_1}(i)$ and $E_{k_2}(i)$, so e.g. using xor with a three-pass-protocol is completely broken.
Oct
16
comment Can we decrypt in this order when the message is encrypted twice?
Search for commutative encryption. There are several related questions on stackoverflow, but you can't trust their answers for security.
Oct
16
comment Can we decrypt in this order when the message is encrypted twice?
You can do it with CTR or OFB. But depending on which intermediate steps an attacker can observe, it's not secure. You need to describe your model, at which points an attacker observes the data clearly. Else you'll end up with a scheme that works but isn't secure.
Oct
15
awarded  Enlightened
Oct
14
awarded  Nice Answer
Oct
14
reviewed Reviewed Encoding numbers that can be decoded mentally?
Oct
14
revised Encoding numbers that can be decoded mentally?
added 3 characters in body
Oct
14
reviewed Reviewed Can one build a one-way function from AES?
Oct
14
revised Can one build a one-way function from AES?
added 47 characters in body
Oct
14
reviewed No Action Needed Where could I submit my algorithm?
Oct
14
comment Using same keypairs for crypt and sign with elliptic curve
Even RSA might allow this, as long as the padding is designed with joint security for signing and encrypting in mind. With blind RSA signatures you can't use the same key for anything else, but you can still reuse the modulus with a different e.
Oct
14
comment Reuse of a DH / ECDH public key
IMO RSA is inferior for most applications. 1) Its private key operation is slower, especially at high security levels. 2) It's size overhead is bigger, both for the encrypted key and for the public key. (32 bytes vs ~300 bytes). 3) It can't authenticate to the recipient without signing (deniable authentication) => I'd only use RSA for legacy application, or when you need its special properties (e.g. blind signatures)
Oct
14
comment PGP encryption options
I'd avoid the old ones (Cast, 3DES, IDEA), and prefer AES or TwoFish. But for all of them, it's unlikely that the strength of symmetric encryption is the weakest point of your system. Spend your time creating a secure end-point and being careful about where you get public keys, rather than worrying about the strength of symmetric ciphers.
Oct
13
comment How long does it take a quantum computer to brute force AES?
@e-sushi If NSA isn't far ahead of D-Wave, then we'll be safe for decades.