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runtime: aeshash, xor seed in earlier

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Instead of doing:

x = input
one round of aes on x
x ^= seed
two rounds of aes on x

Do:

x = input
x ^= seed
three rounds of aes on x

This change provides some additional seed-dependent scrambling
which should help prevent collisions.

Change-Id: I02c774d09c2eb6917cf861513816a1024a9b65d7
Reviewed-on: https://go-review.googlesource.com/23577
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Keith Randall 2016-05-26 08:56:49 -07:00
parent cea29c4a35
commit c83e6f50d9
2 changed files with 82 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

97
src/runtime/asm_amd64.s
View File

@ -914,8 +914,9 @@ aes0to15:
MOVQ $masks<>(SB), AX
PAND (AX)(CX*8), X1
final1:
AESENC X0, X1 // scramble input, xor in seed
AESENC X1, X1 // scramble combo 2 times
PXOR X0, X1 // xor data with seed
AESENC X1, X1 // scramble combo 3 times
AESENC X1, X1
AESENC X1, X1
MOVQ X1, (DX)
RET
@ -949,9 +950,13 @@ aes17to32:
MOVOU (AX), X2
MOVOU -16(AX)(CX*1), X3
// xor with seed
PXOR X0, X2
PXOR X1, X3
// scramble 3 times
AESENC X0, X2
AESENC X1, X3
AESENC X2, X2
AESENC X3, X3
AESENC X2, X2
AESENC X3, X3
AESENC X2, X2
@ -977,11 +982,16 @@ aes33to64:
MOVOU 16(AX), X5
MOVOU -32(AX)(CX*1), X6
MOVOU -16(AX)(CX*1), X7
PXOR X0, X4
PXOR X1, X5
PXOR X2, X6
PXOR X3, X7
AESENC X0, X4
AESENC X1, X5
AESENC X2, X6
AESENC X3, X7
AESENC X4, X4
AESENC X5, X5
AESENC X6, X6
AESENC X7, X7
AESENC X4, X4
AESENC X5, X5
@ -1032,17 +1042,17 @@ aes65to128:
MOVOU -32(AX)(CX*1), X14
MOVOU -16(AX)(CX*1), X15
// scramble data, xor in seed
AESENC X0, X8
AESENC X1, X9
AESENC X2, X10
AESENC X3, X11
AESENC X4, X12
AESENC X5, X13
AESENC X6, X14
AESENC X7, X15
// xor with seed
PXOR X0, X8
PXOR X1, X9
PXOR X2, X10
PXOR X3, X11
PXOR X4, X12
PXOR X5, X13
PXOR X6, X14
PXOR X7, X15
// scramble twice
// scramble 3 times
AESENC X8, X8
AESENC X9, X9
AESENC X10, X10
@ -1051,7 +1061,16 @@ aes65to128:
AESENC X13, X13
AESENC X14, X14
AESENC X15, X15
AESENC X8, X8
AESENC X9, X9
AESENC X10, X10
AESENC X11, X11
AESENC X12, X12
AESENC X13, X13
AESENC X14, X14
AESENC X15, X15
AESENC X8, X8
AESENC X9, X9
AESENC X10, X10
@ -1105,21 +1124,31 @@ aes129plus:
MOVOU -32(AX)(CX*1), X14
MOVOU -16(AX)(CX*1), X15
// scramble input once, xor in seed
AESENC X0, X8
AESENC X1, X9
AESENC X2, X10
AESENC X3, X11
AESENC X4, X12
AESENC X5, X13
AESENC X6, X14
AESENC X7, X15
// xor in seed
PXOR X0, X8
PXOR X1, X9
PXOR X2, X10
PXOR X3, X11
PXOR X4, X12
PXOR X5, X13
PXOR X6, X14
PXOR X7, X15
// compute number of remaining 128-byte blocks
DECQ CX
SHRQ $7, CX
aesloop:
// scramble state
AESENC X8, X8
AESENC X9, X9
AESENC X10, X10
AESENC X11, X11
AESENC X12, X12
AESENC X13, X13
AESENC X14, X14
AESENC X15, X15
// scramble state, xor in a block
MOVOU (AX), X0
MOVOU 16(AX), X1
@ -1138,7 +1167,11 @@ aesloop:
AESENC X6, X14
AESENC X7, X15
// scramble state
ADDQ $128, AX
DECQ CX
JNE aesloop
// 3 more scrambles to finish
AESENC X8, X8
AESENC X9, X9
AESENC X10, X10
@ -1147,12 +1180,6 @@ aesloop:
AESENC X13, X13
AESENC X14, X14
AESENC X15, X15
ADDQ $128, AX
DECQ CX
JNE aesloop
// 2 more scrambles to finish
AESENC X8, X8
AESENC X9, X9
AESENC X10, X10

20
src/runtime/hash_test.go
View File

@ -681,3 +681,23 @@ func BenchmarkUnalignedLoad(b *testing.B) {
}
sink = s
}
func TestCollisions(t *testing.T) {
for i := 0; i < 16; i++ {
for j := 0; j < 16; j++ {
if j == i {
continue
}
var a [16]byte
m := make(map[uint16]struct{}, 1<<16)
for n := 0; n < 1<<16; n++ {
a[i] = byte(n)
a[j] = byte(n >> 8)
m[uint16(BytesHash(a[:], 0))] = struct{}{}
}
if len(m) <= 1<<15 {
t.Errorf("too many collisions i=%d j=%d outputs=%d out of 65536\n", i, j, len(m))
}
}
}
}