func generateMask(rs *random.Source, maskType MaskType, surface Surface) matrix.Matrix {
if maskType == RandomMask {
label := make([]byte, 16)
if surface == Inside {
copy(label[:], []byte("MASK Inside"))
return rs.Matrix(label, 128)
} else {
copy(label[:], []byte("MASK Outside"))
return rs.Matrix(label, 128)
}
} else { // Identity mask.
return matrix.GenerateIdentity(128)
}
}
// Generate byte/word mixing bijections.
// TODO: Ensure that blocks are full-rank.
func MixingBijection(rs *random.Source, size, round, position int) matrix.Matrix {
label := make([]byte, 16)
label[0], label[1], label[2], label[3], label[4] = 'M', 'B', byte(size), byte(round), byte(position)
return rs.Matrix(label, size)
}