k⁻¹ kInv := bigmod.NewNat() inverse(c, kInv, k) Rx, err := R.BytesX() if err != nil { return nil, err } r, err := bigmod.NewNat().SetOverflowingBytes(Rx, c.N) if err != nil { return nil, err } // The spec wants us to retry here, but the chance of hitting this condition // on a large prime-order group like the NIST curves we support is // cryptographically negligible. If we hit it, something is awfully wrong. if r.IsZero() == 1 { return nil, errors.New("ecdsa: internal error: r is zero") } e := bigmod.NewNat()...

k⁻¹ kInv := bigmod.NewNat() inverse(c, kInv, k) Rx, err := R.BytesX() if err != nil { return nil, err } r, err := bigmod.NewNat().SetOverflowingBytes(Rx, c.N) if err != nil { return nil, err } // The spec wants us to retry here, but the chance of hitting this condition // on a large prime-order group like the NIST curves we support is // cryptographically negligible. If we hit it, something is awfully wrong. if r.IsZero() == 1 { return nil, errors.New("ecdsa: internal error: r is zero") } e := bigmod.NewNat()...