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102 lines
2.9 KiB
C++
102 lines
2.9 KiB
C++
#ifndef _SECP256K1_ECDSA_
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#define _SECP256K1_ECDSA_
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namespace secp256k1 {
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bool ParsePubKey(GroupElemJac &elem, const unsigned char *pub, int size) {
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if (size == 33 && (pub[0] == 0x02 || pub[0] == 0x03)) {
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FieldElem x;
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x.SetBytes(pub+1);
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elem.SetCompressed(x, pub[0] == 0x03);
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} else if (size == 65 && (pub[0] == 0x04 || pub[0] == 0x06 || pub[0] == 0x07)) {
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FieldElem x,y;
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x.SetBytes(pub+1);
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y.SetBytes(pub+33);
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elem = GroupElem(x,y);
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if ((pub[0] == 0x06 || pub[0] == 0x07) && y.IsOdd() != (pub[0] == 0x07))
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return false;
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} else {
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return false;
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}
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return elem.IsValid();
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}
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class Signature {
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private:
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Number r,s;
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public:
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Signature(Context &ctx) : r(ctx), s(ctx) {}
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bool Parse(const unsigned char *sig, int size) {
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if (sig[0] != 0x30) return false;
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if (sig[1] != size-2) return false;
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int lenr = sig[3];
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if (4+lenr >= size) return false;
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int lens = sig[lenr+5];
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if (lenr+lens+6 != size) return false;
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if (sig[2] != 0x02) return false;
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if (lenr == 0) return false;
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if (sig[lenr+4] != 0x02) return false;
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if (lens == 0) return false;
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r.SetBytes(sig+4, lenr);
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s.SetBytes(sig+6+lenr, lens);
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return true;
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}
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bool RecomputeR(Context &ctx, Number &r2, const GroupElemJac &pubkey, const Number &message) {
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const GroupConstants &c = GetGroupConst();
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if (r.IsNeg() || s.IsNeg())
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return false;
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if (r.IsZero() || s.IsZero())
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return false;
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if (r.Compare(c.order) >= 0 || s.Compare(c.order) >= 0)
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return false;
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Context ct(ctx);
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Number sn(ct), u1(ct), u2(ct);
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sn.SetModInverse(ct, s, c.order);
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u1.SetModMul(ct, sn, message, c.order);
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u2.SetModMul(ct, sn, r, c.order);
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GroupElemJac pr; ECMult(ct, pr, pubkey, u2, u1);
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if (pr.IsInfinity())
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return false;
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FieldElem xr; pr.GetX(ct, xr);
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unsigned char xrb[32]; xr.GetBytes(xrb);
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r2.SetBytes(xrb,32); r2.SetMod(ct,r2,c.order);
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return true;
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}
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bool Verify(Context &ctx, const GroupElemJac &pubkey, const Number &message) {
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Context ct(ctx);
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Number r2(ct);
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if (!RecomputeR(ct, r2, pubkey, message))
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return false;
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return r2.Compare(r) == 0;
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}
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void SetRS(const Number &rin, const Number &sin) {
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r = rin;
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s = sin;
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}
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};
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int VerifyECDSA(const unsigned char *msg, int msglen, const unsigned char *sig, int siglen, const unsigned char *pubkey, int pubkeylen) {
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Context ctx;
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Number m(ctx);
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Signature s(ctx);
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GroupElemJac q;
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m.SetBytes(msg, msglen);
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if (!ParsePubKey(q, pubkey, pubkeylen))
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return -1;
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if (!s.Parse(sig, siglen))
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return -2;
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if (!s.Verify(ctx, q, m))
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return 0;
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return 1;
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}
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}
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#endif
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