an invalid value") } return } } // Calculate the inverse of s in GF(N) using Fermat's method // (exponentiation modulo P - 2, per Euler's theorem) kInv.Exp(k, c.nMinus2, c.N) } // hashToNat sets e to the left-most bits of hash, according to // FIPS 186-5, Section 6.4.1, point 2 and Section 6.4.2, point 3. func hashToNat[P Point[P]](c *Curve[P], e *bigmod.Nat, hash []byte) { // ECDSA asks us to take the left-most log2(N) bits of hash, and use them as // an integer modulo N. This is the absolute worst...