On 17/04/12 06:57, toredhiddenu...@tormail.net wrote:
The library only supports Fp and F2^m custom curves. The easiest way to
construct a custom curve is by using one of:
EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a, const
BIGNUM *b, BN_CTX *ctx);
EC_GROUP *EC_GROUP_new_curve_GF2m(const BIGNUM *p, const BIGNUM *a,
const BIGNUM *b, BN_CTX *ctx);
Where for an Fp curve p, a and b are used as follows:
y^2 mod p = x^3 +ax + b mod p
And for an F2^m curve p (p=2^m), a and b are:
y^2 + xy mod p = x^3 + ax^2 + b (where b != 0) mod p
Matt
So, do you say it can't be done with executable?
Will this be a feature in future releases?
Are you sure there's no way to do that than digging the C
source?
Well ultimately openssl is a library. The functions I mention above are
part of the public API so you don't need to modify the openssl source to
use them. It does require programming though.
From your question I assume you are referring to the openssl command
line tool. I am not particularly familiar with the command line tool as
most of my work has been with the library directly. However I would be
surprised if you can define custom curves using it...that's fairly
advanced stuff that most users are never going to need to use (nor would
it be advisable for them to do so). In almost all cases using a standard
curve will be sufficient - and its by far the safest option.
In terms of future support for new curves, I imagine that is going to be
driven by the standards. As curves get defined and standardised they
will work their way into openssl.
Matt
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