9,467 reputation
12346
bio website github.com/CodesInChaos
location Frankfurt, Germany
age
visits member for 3 years
seen 47 mins ago

Oct
1
comment How to calculate y value from ((y*y) mod prime) efficiently
Mathematical routines for the NIST prime elliptic curves describes an algorithm for modular square roots as required by NIST P-224. "Routines 3.2.4, 3.2.5, 3.2.6, and 3.2.7 are all auxilliary to 3.2.8, which is used to compute square roots modulo p 224 . The method is based on an algorithm of Pocklington described in [Ber]." which refers to Bernstein - Faster square roots in annoying finite fields
Oct
1
comment how to iteratively calculate a^emod n with modulus n sized 4096 bits
Accelerating public key operations sees a bit unusual. Typically it's the private key operation that needs acceleration since it's 100x as expensive. If performance of public key operations is really an issue, I'd consider using e=3
Oct
1
comment how to iteratively calculate a^emod n with modulus n sized 4096 bits
You might be able to use CRT together with multi-prime RSA.
Oct
1
comment Hybrid encryption with RSA and AES versus spliting into multiple RSA messages?
@Markus Why don't you simply use TLS with client certificates?
Oct
1
comment Why are cryptography algorithms not exported to certain countries?
1) It's just politicians being behind the times. Of course copying open source crypto is trivial for those countries. 2) For most algorithms it's extremely unlikely that they were backdoored 3) Writing your own implementation is risky. Most crypto code I've seen is broken, even when it builds on standard primitives like AES.
Oct
1
comment Hybrid encryption with RSA and AES versus spliting into multiple RSA messages?
@Markus I don't understand what you're doing, but it's probably a bad idea.
Oct
1
comment Hybrid encryption with RSA and AES versus spliting into multiple RSA messages?
Don't forget to include a MAC, else active attacks will break your scheme. Personally I'd go with NaCl's box operation instead of building my own hybrid encryption scheme.
Oct
1
reviewed Approve suggested edit on ripemd tag wiki excerpt
Oct
1
reviewed Approve suggested edit on ripemd tag wiki
Sep
30
comment Is it possible to create an open-source SecurID?
What prevents public key crypto is that the tokens are so short. As algorithm you could use the standard TOTP
Sep
28
comment understanding pairing $e:G \times G \to G_T$ and ( Decision)BDH assumption
As long as you use a secure pairing friendly curve, it should be secure. Curves with a pairing to a binary field have been seriously weakened recently and should be avoided.
Sep
28
reviewed Satisfactory Relationship between Elliptic Curve Discrete Log, Integer Discrete Log, and Integer Factorization
Sep
28
reviewed Satisfactory Generate Elliptic Curve Private Key from User Passphrase?
Sep
28
reviewed Excellent How relevant are hardware implementations of crypto algorithms?
Sep
28
reviewed Satisfactory Will our app be FIPS 140-2 compliant if we use our own AES algorithm implementation?
Sep
28
reviewed Excellent What criteria make the theta step of Keccak's round function reversible?
Sep
28
reviewed Satisfactory Does the GCM authentication tag need to be protected?
Sep
28
reviewed Satisfactory How to supply the GCM authentication tag to the OpenSSL command line tools?
Sep
28
reviewed Satisfactory Does there exist a two-pass AKE protocol that is secure in eCK model and also has PFS?
Sep
28
reviewed Excellent Is it theoretically possible to construct a string that contain its own hash value?