sha1block.go

     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
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