INNER CODE UNIT · Go

SplitScalar

Consensys/gnark-crypto · ecc/utils.go:243

func SplitScalar(s *big.Int, l *Lattice) [2]big.Int {

	var k1, k2 big.Int
	k1.Mul(s, &l.b1)
	k2.Mul(s, &l.b2).Neg(&k2)
	// right-shift instead of division by lattice determinant
	// this increases the bounds on k1 and k2 by 1
	// but we check this ScalarMultiplication alg. (not constant-time)
	n := 2 * uint(((l.Det.BitLen()+32)>>6)<<6)
	k1.Rsh(&k1, n)
	k2.Rsh(&k2, n)
	v := getVector(l, &k1, &k2)
	v[0].Sub(s, &v[0])
	v[1].Neg(&v[1])
	return v
}

// SplitScalarFour computes k0,k1,k2,k3 such that

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