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how to define total length of ECC F2M 571bits signture
Posted: Wed Nov 04, 2015 7:30 am
by BirdKing
Hello,
when I compute a signature of ecc f2m 571bits, I get a result. But the result's length greater than 0x80. how to define total length of ECC F2M 571bits signture?
Re: how to define total length of ECC F2M 571bits signture
Posted: Thu Nov 05, 2015 11:23 pm
by UNKNwYSHSA
Have you tried to calculate the signature of this bits length using openssl?
Re: how to define total length of ECC F2M 571bits signture
Posted: Fri Nov 06, 2015 12:22 am
by BirdKing
UNKNwYSHSA wrote:Have you tried to calculate the signature of this bits length using openssl?
yes. I got a signature such as "30 81 94 02 ...".
Re: how to define total length of ECC F2M 571bits signture
Posted: Fri Nov 06, 2015 2:24 am
by UNKNwYSHSA
BirdKing wrote:UNKNwYSHSA wrote:Have you tried to calculate the signature of this bits length using openssl?
yes. I got a signature such as "30 81 94 02 ...".
Please show me all signature data bytes!
Re: how to define total length of ECC F2M 571bits signture
Posted: Wed Nov 11, 2015 2:14 am
by UNKNwYSHSA
Here is the implement of function ECDSA_sign in openssl:
Code: Select all
int ECDSA_sign_ex(int type, const unsigned char *dgst, int dlen, unsigned char
*sig, unsigned int *siglen, const BIGNUM *kinv, const BIGNUM *r,
EC_KEY *eckey)
{
ECDSA_SIG *s;
RAND_seed(dgst, dlen);
s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
if (s == NULL)
{
*siglen=0;
return 0;
}
*siglen = i2d_ECDSA_SIG(s, &sig);
ECDSA_SIG_free(s);
return 1;
}
The signature data is encoded with DER format.
You can use the decode function
to decode signature data.
Wait your message.
Re: how to define total length of ECC F2M 571bits signture
Posted: Tue Nov 17, 2015 4:34 am
by BirdKing
Thank you for your help.
I finally understood how to struct the R and S. Following the TLV, I can get the right signature.
Thank everybody.