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utils.go
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/
utils.go
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package sm4
import (
"math/bits"
"encoding/binary"
)
// Endianness option
const littleEndian bool = false
func getu32(ptr []byte) uint32 {
if littleEndian {
return binary.LittleEndian.Uint32(ptr)
} else {
return binary.BigEndian.Uint32(ptr)
}
}
func putu32(ptr []byte, a uint32) {
if littleEndian {
binary.LittleEndian.PutUint32(ptr, a)
} else {
binary.BigEndian.PutUint32(ptr, a)
}
}
func bytesToUint32s(b []byte) []uint32 {
size := len(b) / 4
dst := make([]uint32, size)
for i := 0; i < size; i++ {
j := i * 4
if littleEndian {
dst[i] = binary.LittleEndian.Uint32(b[j:])
} else {
dst[i] = binary.BigEndian.Uint32(b[j:])
}
}
return dst
}
func uint32sToBytes(w []uint32) []byte {
size := len(w) * 4
dst := make([]byte, size)
for i := 0; i < len(w); i++ {
j := i * 4
if littleEndian {
binary.LittleEndian.PutUint32(dst[j:], w[i])
} else {
binary.BigEndian.PutUint32(dst[j:], w[i])
}
}
return dst
}
func rotl(a uint32, n int) uint32 {
return bits.RotateLeft32(a, n)
}
func tau(b uint32) uint32 {
var in [4]byte
var out [4]byte
putu32(in[:], b)
out[0] = sbox[in[0]]
out[1] = sbox[in[1]]
out[2] = sbox[in[2]]
out[3] = sbox[in[3]]
return getu32(out[:])
}
// L
func l(b uint32) uint32 {
return b ^
rotl(b, 2) ^
rotl(b, 10) ^
rotl(b, 18) ^
rotl(b, 24)
}
// L2
func lAp(b uint32) uint32 {
return b ^ rotl(b, 13) ^ rotl(b, 23)
}
// T
func tSlow(X uint32) uint32 {
// L linear transform
return l(tau(X))
}
// t(X) equal tSlow(X)
// t(X) run fast
func t(X uint32) uint32 {
var in [4]byte
putu32(in[:], X)
return sbox_t0[in[0]] ^
sbox_t1[in[1]] ^
sbox_t2[in[2]] ^
sbox_t3[in[3]]
}
// T'
func keySub(X uint32) uint32 {
return lAp(tau(X))
}