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crypto/aes: eliminate some bounds checking and manual truncation.

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By converting array indices to uint8, they are automatically
constrained in the array range, and the binary AND with 0xff
is no longer needed anymore.

Before:  aes.BenchmarkEncrypt    363 ns/op
After:   aes.BenchmarkEncrypt    273 ns/op

R=golang-dev, gri, agl
CC=golang-dev, remy
https://golang.org/cl/5450084
This commit is contained in:
Rémy Oudompheng 2011-12-05 13:30:25 -05:00 committed by Adam Langley
parent b9ccd077dc
commit 3538d40ab5
2 changed files with 22 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/pkg/crypto/aes/aes_test.go
View File

@ -348,3 +348,17 @@ func TestCipherDecrypt(t *testing.T) {
}
}
}
func BenchmarkEncrypt(b *testing.B) {
b.StopTimer()
tt := encryptTests[0]
c, err := NewCipher(tt.key)
if err != nil {
panic("NewCipher")
}
out := make([]byte, len(tt.in))
b.StartTimer()
for i := 0; i < b.N; i++ {
c.Encrypt(out, tt.in)
}
}

16
src/pkg/crypto/aes/block.go
View File

@ -56,10 +56,10 @@ func encryptBlock(xk []uint32, dst, src []byte) {
nr := len(xk)/4 - 2 // - 2: one above, one more below
k := 4
for r := 0; r < nr; r++ {
t0 = xk[k+0] ^ te[0][s0>>24] ^ te[1][s1>>16&0xff] ^ te[2][s2>>8&0xff] ^ te[3][s3&0xff]
t1 = xk[k+1] ^ te[0][s1>>24] ^ te[1][s2>>16&0xff] ^ te[2][s3>>8&0xff] ^ te[3][s0&0xff]
t2 = xk[k+2] ^ te[0][s2>>24] ^ te[1][s3>>16&0xff] ^ te[2][s0>>8&0xff] ^ te[3][s1&0xff]
t3 = xk[k+3] ^ te[0][s3>>24] ^ te[1][s0>>16&0xff] ^ te[2][s1>>8&0xff] ^ te[3][s2&0xff]
t0 = xk[k+0] ^ te[0][uint8(s0>>24)] ^ te[1][uint8(s1>>16)] ^ te[2][uint8(s2>>8)] ^ te[3][uint8(s3)]
t1 = xk[k+1] ^ te[0][uint8(s1>>24)] ^ te[1][uint8(s2>>16)] ^ te[2][uint8(s3>>8)] ^ te[3][uint8(s0)]
t2 = xk[k+2] ^ te[0][uint8(s2>>24)] ^ te[1][uint8(s3>>16)] ^ te[2][uint8(s0>>8)] ^ te[3][uint8(s1)]
t3 = xk[k+3] ^ te[0][uint8(s3>>24)] ^ te[1][uint8(s0>>16)] ^ te[2][uint8(s1>>8)] ^ te[3][uint8(s2)]
k += 4
s0, s1, s2, s3 = t0, t1, t2, t3
}
@ -101,10 +101,10 @@ func decryptBlock(xk []uint32, dst, src []byte) {
nr := len(xk)/4 - 2 // - 2: one above, one more below
k := 4
for r := 0; r < nr; r++ {
t0 = xk[k+0] ^ td[0][s0>>24] ^ td[1][s3>>16&0xff] ^ td[2][s2>>8&0xff] ^ td[3][s1&0xff]
t1 = xk[k+1] ^ td[0][s1>>24] ^ td[1][s0>>16&0xff] ^ td[2][s3>>8&0xff] ^ td[3][s2&0xff]
t2 = xk[k+2] ^ td[0][s2>>24] ^ td[1][s1>>16&0xff] ^ td[2][s0>>8&0xff] ^ td[3][s3&0xff]
t3 = xk[k+3] ^ td[0][s3>>24] ^ td[1][s2>>16&0xff] ^ td[2][s1>>8&0xff] ^ td[3][s0&0xff]
t0 = xk[k+0] ^ td[0][uint8(s0>>24)] ^ td[1][uint8(s3>>16)] ^ td[2][uint8(s2>>8)] ^ td[3][uint8(s1)]
t1 = xk[k+1] ^ td[0][uint8(s1>>24)] ^ td[1][uint8(s0>>16)] ^ td[2][uint8(s3>>8)] ^ td[3][uint8(s2)]
t2 = xk[k+2] ^ td[0][uint8(s2>>24)] ^ td[1][uint8(s1>>16)] ^ td[2][uint8(s0>>8)] ^ td[3][uint8(s3)]
t3 = xk[k+3] ^ td[0][uint8(s3>>24)] ^ td[1][uint8(s2>>16)] ^ td[2][uint8(s1>>8)] ^ td[3][uint8(s0)]
k += 4
s0, s1, s2, s3 = t0, t1, t2, t3
}