Nonce usage in ECDSA signing algorithm I'm trying to understand the signing function secp256k1_ecdsa_sig_sign(), and I'm curious about the nonce usage here. static int secp256k1_ecdsa_sig_sign(const secp256k1_ecmult_gen_context *ctx, secp256k1_scalar *sigr, secp256k1_scalar *sigs, const secp256k1_scalar *seckey, const secp256k1_scalar *message, const secp256k1_scalar *nonce, int *recid) { unsigned char b[32]; secp256k1_gej rp; secp256k1_ge r; secp256k1_scalar n; int overflow = 0; secp256k1_ecmult_gen(ctx, &rp, nonce); secp256k1_ge_set_gej(&r, &rp); secp256k1_fe_normalize(&r.x); secp256k1_fe_normalize(&r.y); secp256k1_fe_get_b32(b, &r.x); secp256k1_scalar_set_b32(sigr, b, &overflow); /* These two conditions should be checked before calling */ VERIFY_CHECK(!secp256k1_scalar_is_zero(sigr)); VERIFY_CHECK(overflow == 0); if (recid) { /* The overflow condition is cryptographically unreachable as hitting it requires f...
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