1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 package sha1
6 7 import (
8 "math/bits"
9 )
10 11 const (
12 _K0 = 0x5A827999
13 _K1 = 0x6ED9EBA1
14 _K2 = 0x8F1BBCDC
15 _K3 = 0xCA62C1D6
16 )
17 18 // blockGeneric is a portable, pure Go version of the SHA-1 block step.
19 // It's used by sha1block_generic.go and tests.
20 func blockGeneric(dig *digest, p []byte) {
21 var w [16]uint32
22 23 h0, h1, h2, h3, h4 := dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4]
24 for len(p) >= chunk {
25 // Can interlace the computation of w with the
26 // rounds below if needed for speed.
27 for i := 0; i < 16; i++ {
28 j := i * 4
29 w[i] = uint32(p[j])<<24 | uint32(p[j+1])<<16 | uint32(p[j+2])<<8 | uint32(p[j+3])
30 }
31 32 a, b, c, d, e := h0, h1, h2, h3, h4
33 34 // Each of the four 20-iteration rounds
35 // differs only in the computation of f and
36 // the choice of K (_K0, _K1, etc).
37 i := 0
38 for ; i < 16; i++ {
39 f := b&c | (^b)&d
40 t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + _K0
41 a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
42 }
43 for ; i < 20; i++ {
44 tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
45 w[i&0xf] = bits.RotateLeft32(tmp, 1)
46 47 f := b&c | (^b)&d
48 t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + _K0
49 a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
50 }
51 for ; i < 40; i++ {
52 tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
53 w[i&0xf] = bits.RotateLeft32(tmp, 1)
54 f := b ^ c ^ d
55 t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + _K1
56 a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
57 }
58 for ; i < 60; i++ {
59 tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
60 w[i&0xf] = bits.RotateLeft32(tmp, 1)
61 f := ((b | c) & d) | (b & c)
62 t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + _K2
63 a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
64 }
65 for ; i < 80; i++ {
66 tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
67 w[i&0xf] = bits.RotateLeft32(tmp, 1)
68 f := b ^ c ^ d
69 t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + _K3
70 a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
71 }
72 73 h0 += a
74 h1 += b
75 h2 += c
76 h3 += d
77 h4 += e
78 79 p = p[chunk:]
80 }
81 82 dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4] = h0, h1, h2, h3, h4
83 }
84