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recover public key from GOST R 34.10 signature

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orignal 2017-03-26 08:55:15 -04:00
parent 69804c23f1
commit 8e558f0826
2 changed files with 33 additions and 0 deletions
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32
Gost.cpp
View File

@ -96,6 +96,38 @@ namespace crypto
return ret;
}
EC_POINT * GOSTR3410Curve::RecoverPublicKey (const BIGNUM * digest, const BIGNUM * r, const BIGNUM * s, bool isNegativeY) const
{
// s*P = r*Q + h*C
BN_CTX * ctx = BN_CTX_new ();
BN_CTX_start (ctx);
EC_POINT * C = EC_POINT_new (m_Group); // C = k*P = (rx, ry)
EC_POINT * Q = nullptr;
if (EC_POINT_set_compressed_coordinates_GFp (m_Group, C, r, isNegativeY ? 1 : 0, ctx))
{
EC_POINT * S = EC_POINT_new (m_Group); // S = s*P
EC_POINT_mul (m_Group, S, s, nullptr, nullptr, ctx);
BIGNUM * q = BN_CTX_get (ctx);
EC_GROUP_get_order(m_Group, q, ctx);
BIGNUM * h = BN_CTX_get (ctx);
BN_mod (h, digest, q, ctx); // h = digest % q
BN_sub (h, q, h); // h = -h
EC_POINT * H = EC_POINT_new (m_Group);
EC_POINT_mul (m_Group, H, nullptr, C, h, ctx); // -h*C
EC_POINT_add (m_Group, C, S, H, ctx); // s*P - h*C
EC_POINT_free (H);
EC_POINT_free (S);
BIGNUM * r1 = BN_CTX_get (ctx);
BN_mod_inverse (r1, r, q, ctx);
Q = EC_POINT_new (m_Group);
EC_POINT_mul (m_Group, Q, nullptr, C, r1, ctx); // (s*P - h*C)/r
}
EC_POINT_free (C);
BN_CTX_end (ctx);
BN_CTX_free (ctx);
return Q;
}
static GOSTR3410Curve * CreateGOSTR3410Curve (GOSTR3410ParamSet paramSet)
{
// a, b, p, q, x, y

1
Gost.h
View File

@ -35,6 +35,7 @@ namespace crypto
EC_POINT * CreatePoint (const BIGNUM * x, const BIGNUM * y) const;
void Sign (const BIGNUM * priv, const BIGNUM * digest, BIGNUM * r, BIGNUM * s);
bool Verify (const EC_POINT * pub, const BIGNUM * digest, const BIGNUM * r, const BIGNUM * s);
EC_POINT * RecoverPublicKey (const BIGNUM * digest, const BIGNUM * r, const BIGNUM * s, bool isNegativeY = false) const;
private: