if c.curve.Params().Name == "P-256" {
		kBytes, err := nistec.P256OrdInverse(k.Bytes(c.N))
		// Some platforms don't implement P256OrdInverse, and always return an error.
		if err == nil {
			_, err := kInv.SetBytes(kBytes, c.N)
			if err != nil {
				panic("ecdsa: internal error: P256OrdInverse produced an invalid value")
			}
			return
		}
	}

func (p *P256Point) SetBytes(b []byte) (*P256Point, error) {
	// p256Mul operates in the Montgomery domain with R = 2²⁵⁶ mod p. Thus rr
	// here is R in the Montgomery domain, or R×R mod p. See comment in
	// P256OrdInverse about how this is used.
	rr := p256Element{0x0000000000000003, 0xfffffffbffffffff,
		0xfffffffffffffffe, 0x00000004fffffffd}

	switch {
	// Point at infinity.
	case len(b) == 1 && b[0] == 0: