crypto/twofish: update with rsc's comments
TBR=rsc
R=rsc
CC=berengar.lehr, golang-dev
https://golang.org/cl/4050042
diff --git a/src/pkg/crypto/twofish/twofish.go b/src/pkg/crypto/twofish/twofish.go
index b362c44..62253e7 100644
--- a/src/pkg/crypto/twofish/twofish.go
+++ b/src/pkg/crypto/twofish/twofish.go
@@ -51,9 +51,9 @@
var S [4 * 4]byte
for i := 0; i < k; i++ {
// Computes [y0 y1 y2 y3] = rs . [x0 x1 x2 x3 x4 x5 x6 x7]
- for j := 0; j < 4; j++ {
- for k := 0; k < 8; k++ {
- S[4*i+j] ^= gfMult(key[8*i+k], rs[j][k], rsPolynomial)
+ for j, rsRow := range rs {
+ for k, rsVal := range rsRow {
+ S[4*i+j] ^= gfMult(key[8*i+k], rsVal, rsPolynomial)
}
}
}
@@ -63,13 +63,13 @@
var tmp [4]byte
for i := byte(0); i < 20; i++ {
// A = h(p * 2x, Me)
- for j := 0; j < 4; j++ {
+ for j := range tmp {
tmp[j] = 2 * i
}
A := h(tmp[:], key, 0)
// B = rolc(h(p * (2x + 1), Mo), 8)
- for j := 0; j < 4; j++ {
+ for j := range tmp {
tmp[j] = 2*i + 1
}
B := h(tmp[:], key, 1)
@@ -84,21 +84,21 @@
// Calculate sboxes
switch k {
case 2:
- for i := 0; i <= 255; i++ {
+ for i := range c.s[0] {
c.s[0][i] = mdsColumnMult(sbox[1][sbox[0][sbox[0][byte(i)]^S[0]]^S[4]], 0)
c.s[1][i] = mdsColumnMult(sbox[0][sbox[0][sbox[1][byte(i)]^S[1]]^S[5]], 1)
c.s[2][i] = mdsColumnMult(sbox[1][sbox[1][sbox[0][byte(i)]^S[2]]^S[6]], 2)
c.s[3][i] = mdsColumnMult(sbox[0][sbox[1][sbox[1][byte(i)]^S[3]]^S[7]], 3)
}
case 3:
- for i := 0; i < 256; i++ {
+ for i := range c.s[0] {
c.s[0][i] = mdsColumnMult(sbox[1][sbox[0][sbox[0][sbox[1][byte(i)]^S[0]]^S[4]]^S[8]], 0)
c.s[1][i] = mdsColumnMult(sbox[0][sbox[0][sbox[1][sbox[1][byte(i)]^S[1]]^S[5]]^S[9]], 1)
c.s[2][i] = mdsColumnMult(sbox[1][sbox[1][sbox[0][sbox[0][byte(i)]^S[2]]^S[6]]^S[10]], 2)
c.s[3][i] = mdsColumnMult(sbox[0][sbox[1][sbox[1][sbox[0][byte(i)]^S[3]]^S[7]]^S[11]], 3)
}
default:
- for i := 0; i < 256; i++ {
+ for i := range c.s[0] {
c.s[0][i] = mdsColumnMult(sbox[1][sbox[0][sbox[0][sbox[1][sbox[1][byte(i)]^S[0]]^S[4]]^S[8]]^S[12]], 0)
c.s[1][i] = mdsColumnMult(sbox[0][sbox[0][sbox[1][sbox[1][sbox[0][byte(i)]^S[1]]^S[5]]^S[9]]^S[13]], 1)
c.s[2][i] = mdsColumnMult(sbox[1][sbox[1][sbox[0][sbox[0][sbox[0][byte(i)]^S[2]]^S[6]]^S[10]]^S[14]], 2)
@@ -112,10 +112,10 @@
// Reset zeros the key data, so that it will no longer appear in the process's
// memory.
func (c *Cipher) Reset() {
- for i := 0; i < 40; i++ {
+ for i := range c.k {
c.k[i] = 0
}
- for i := 0; i < 4; i++ {
+ for i := range c.s {
for j := 0; j < 265; j++ {
c.s[i][j] = 0
}
@@ -213,7 +213,7 @@
return byte(result)
}
-// mdsColumnMult calculates y{col} where [y0 y1 y2 y3] = MDS . [x0]
+// mdsColumnMult calculates y{col} where [y0 y1 y2 y3] = MDS · [x0]
func mdsColumnMult(in byte, col int) uint32 {
mul01 := in
mul5B := gfMult(in, 0x5B, mdsPolynomial)
@@ -236,7 +236,7 @@
// h implements the S-box generation function. See [TWOFISH] 4.3.5
func h(in, key []byte, offset int) uint32 {
var y [4]byte
- for x := 0; x < 4; x++ {
+ for x := range y {
y[x] = in[x]
}
switch len(key) / 8 {
@@ -260,7 +260,7 @@
}
// [y0 y1 y2 y3] = MDS . [x0 x1 x2 x3]
var mdsMult uint32
- for i := 0; i < 4; i++ {
+ for i := range y {
mdsMult ^= mdsColumnMult(y[i], i)
}
return mdsMult
@@ -270,42 +270,42 @@
// Note that for amounts of data larger than a block,
// it is not safe to just call Encrypt on successive blocks;
// instead, use an encryption mode like CBC (see crypto/block/cbc.go).
-func (skey *Cipher) Encrypt(dst, src []byte) {
- S1 := skey.s[0]
- S2 := skey.s[1]
- S3 := skey.s[2]
- S4 := skey.s[3]
+func (c *Cipher) Encrypt(dst, src []byte) {
+ S1 := c.s[0]
+ S2 := c.s[1]
+ S3 := c.s[2]
+ S4 := c.s[3]
// Load input
- a := load32l(src[0:4])
- b := load32l(src[4:8])
- c := load32l(src[8:12])
- d := load32l(src[12:16])
+ ia := load32l(src[0:4])
+ ib := load32l(src[4:8])
+ ic := load32l(src[8:12])
+ id := load32l(src[12:16])
// Pre-whitening
- a ^= skey.k[0]
- b ^= skey.k[1]
- c ^= skey.k[2]
- d ^= skey.k[3]
+ ia ^= c.k[0]
+ ib ^= c.k[1]
+ ic ^= c.k[2]
+ id ^= c.k[3]
for i := 0; i < 8; i++ {
- k := skey.k[8+i*4 : 12+i*4]
- t2 := S2[byte(b)] ^ S3[byte(b>>8)] ^ S4[byte(b>>16)] ^ S1[byte(b>>24)]
- t1 := S1[byte(a)] ^ S2[byte(a>>8)] ^ S3[byte(a>>16)] ^ S4[byte(a>>24)] + t2
- c = ror(c^(t1+k[0]), 1)
- d = rol(d, 1) ^ (t2 + t1 + k[1])
+ k := c.k[8+i*4 : 12+i*4]
+ t2 := S2[byte(ib)] ^ S3[byte(ib>>8)] ^ S4[byte(ib>>16)] ^ S1[byte(ib>>24)]
+ t1 := S1[byte(ia)] ^ S2[byte(ia>>8)] ^ S3[byte(ia>>16)] ^ S4[byte(ia>>24)] + t2
+ ic = ror(ic^(t1+k[0]), 1)
+ id = rol(id, 1) ^ (t2 + t1 + k[1])
- t2 = S2[byte(d)] ^ S3[byte(d>>8)] ^ S4[byte(d>>16)] ^ S1[byte(d>>24)]
- t1 = S1[byte(c)] ^ S2[byte(c>>8)] ^ S3[byte(c>>16)] ^ S4[byte(c>>24)] + t2
- a = ror(a^(t1+k[2]), 1)
- b = rol(b, 1) ^ (t2 + t1 + k[3])
+ t2 = S2[byte(id)] ^ S3[byte(id>>8)] ^ S4[byte(id>>16)] ^ S1[byte(id>>24)]
+ t1 = S1[byte(ic)] ^ S2[byte(ic>>8)] ^ S3[byte(ic>>16)] ^ S4[byte(ic>>24)] + t2
+ ia = ror(ia^(t1+k[2]), 1)
+ ib = rol(ib, 1) ^ (t2 + t1 + k[3])
}
// Output with "undo last swap"
- ta := c ^ skey.k[4]
- tb := d ^ skey.k[5]
- tc := a ^ skey.k[6]
- td := b ^ skey.k[7]
+ ta := ic ^ c.k[4]
+ tb := id ^ c.k[5]
+ tc := ia ^ c.k[6]
+ td := ib ^ c.k[7]
store32l(dst[0:4], ta)
store32l(dst[4:8], tb)
@@ -314,11 +314,11 @@
}
// Decrypt decrypts a 16-byte block from src to dst, which may overlap.
-func (skey *Cipher) Decrypt(dst, src []byte) {
- S1 := skey.s[0]
- S2 := skey.s[1]
- S3 := skey.s[2]
- S4 := skey.s[3]
+func (c *Cipher) Decrypt(dst, src []byte) {
+ S1 := c.s[0]
+ S2 := c.s[1]
+ S3 := c.s[2]
+ S4 := c.s[3]
// Load input
ta := load32l(src[0:4])
@@ -327,32 +327,32 @@
td := load32l(src[12:16])
// Undo undo final swap
- a := tc ^ skey.k[6]
- b := td ^ skey.k[7]
- c := ta ^ skey.k[4]
- d := tb ^ skey.k[5]
+ ia := tc ^ c.k[6]
+ ib := td ^ c.k[7]
+ ic := ta ^ c.k[4]
+ id := tb ^ c.k[5]
for i := 8; i > 0; i-- {
- k := skey.k[4+i*4 : 8+i*4]
- t2 := S2[byte(d)] ^ S3[byte(d>>8)] ^ S4[byte(d>>16)] ^ S1[byte(d>>24)]
- t1 := S1[byte(c)] ^ S2[byte(c>>8)] ^ S3[byte(c>>16)] ^ S4[byte(c>>24)] + t2
- a = rol(a, 1) ^ (t1 + k[2])
- b = ror(b^(t2+t1+k[3]), 1)
+ k := c.k[4+i*4 : 8+i*4]
+ t2 := S2[byte(id)] ^ S3[byte(id>>8)] ^ S4[byte(id>>16)] ^ S1[byte(id>>24)]
+ t1 := S1[byte(ic)] ^ S2[byte(ic>>8)] ^ S3[byte(ic>>16)] ^ S4[byte(ic>>24)] + t2
+ ia = rol(ia, 1) ^ (t1 + k[2])
+ ib = ror(ib^(t2+t1+k[3]), 1)
- t2 = S2[byte(b)] ^ S3[byte(b>>8)] ^ S4[byte(b>>16)] ^ S1[byte(b>>24)]
- t1 = S1[byte(a)] ^ S2[byte(a>>8)] ^ S3[byte(a>>16)] ^ S4[byte(a>>24)] + t2
- c = rol(c, 1) ^ (t1 + k[0])
- d = ror(d^(t2+t1+k[1]), 1)
+ t2 = S2[byte(ib)] ^ S3[byte(ib>>8)] ^ S4[byte(ib>>16)] ^ S1[byte(ib>>24)]
+ t1 = S1[byte(ia)] ^ S2[byte(ia>>8)] ^ S3[byte(ia>>16)] ^ S4[byte(ia>>24)] + t2
+ ic = rol(ic, 1) ^ (t1 + k[0])
+ id = ror(id^(t2+t1+k[1]), 1)
}
// Undo pre-whitening
- a ^= skey.k[0]
- b ^= skey.k[1]
- c ^= skey.k[2]
- d ^= skey.k[3]
+ ia ^= c.k[0]
+ ib ^= c.k[1]
+ ic ^= c.k[2]
+ id ^= c.k[3]
- store32l(dst[0:4], a)
- store32l(dst[4:8], b)
- store32l(dst[8:12], c)
- store32l(dst[12:16], d)
+ store32l(dst[0:4], ia)
+ store32l(dst[4:8], ib)
+ store32l(dst[8:12], ic)
+ store32l(dst[12:16], id)
}
diff --git a/src/pkg/crypto/twofish/twofish_test.go b/src/pkg/crypto/twofish/twofish_test.go
index 96ca679..303081f 100644
--- a/src/pkg/crypto/twofish/twofish_test.go
+++ b/src/pkg/crypto/twofish/twofish_test.go
@@ -37,8 +37,8 @@
}
func TestSbox(t *testing.T) {
- for n := 0; n < 2; n++ {
- for m := 0; m < 256; m++ {
+ for n := range sbox {
+ for m := range sbox[n] {
if genSbox(n, byte(m)) != sbox[n][m] {
t.Errorf("#%d|%d: sbox value = %d want %d", n, m, sbox[n][m], genSbox(n, byte(m)))
}
