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Source file src/crypto/sha1/sha1block.go

Documentation: crypto/sha1

     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  const (
     8  	_K0 = 0x5A827999
     9  	_K1 = 0x6ED9EBA1
    10  	_K2 = 0x8F1BBCDC
    11  	_K3 = 0xCA62C1D6
    12  )
    13  
    14  // blockGeneric is a portable, pure Go version of the SHA-1 block step.
    15  // It's used by sha1block_generic.go and tests.
    16  func blockGeneric(dig *digest, p []byte) {
    17  	var w [16]uint32
    18  
    19  	h0, h1, h2, h3, h4 := dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4]
    20  	for len(p) >= chunk {
    21  		// Can interlace the computation of w with the
    22  		// rounds below if needed for speed.
    23  		for i := 0; i < 16; i++ {
    24  			j := i * 4
    25  			w[i] = uint32(p[j])<<24 | uint32(p[j+1])<<16 | uint32(p[j+2])<<8 | uint32(p[j+3])
    26  		}
    27  
    28  		a, b, c, d, e := h0, h1, h2, h3, h4
    29  
    30  		// Each of the four 20-iteration rounds
    31  		// differs only in the computation of f and
    32  		// the choice of K (_K0, _K1, etc).
    33  		i := 0
    34  		for ; i < 16; i++ {
    35  			f := b&c | (^b)&d
    36  			a5 := a<<5 | a>>(32-5)
    37  			b30 := b<<30 | b>>(32-30)
    38  			t := a5 + f + e + w[i&0xf] + _K0
    39  			a, b, c, d, e = t, a, b30, c, d
    40  		}
    41  		for ; i < 20; i++ {
    42  			tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
    43  			w[i&0xf] = tmp<<1 | tmp>>(32-1)
    44  
    45  			f := b&c | (^b)&d
    46  			a5 := a<<5 | a>>(32-5)
    47  			b30 := b<<30 | b>>(32-30)
    48  			t := a5 + f + e + w[i&0xf] + _K0
    49  			a, b, c, d, e = t, a, b30, 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] = tmp<<1 | tmp>>(32-1)
    54  			f := b ^ c ^ d
    55  			a5 := a<<5 | a>>(32-5)
    56  			b30 := b<<30 | b>>(32-30)
    57  			t := a5 + f + e + w[i&0xf] + _K1
    58  			a, b, c, d, e = t, a, b30, c, d
    59  		}
    60  		for ; i < 60; i++ {
    61  			tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
    62  			w[i&0xf] = tmp<<1 | tmp>>(32-1)
    63  			f := ((b | c) & d) | (b & c)
    64  
    65  			a5 := a<<5 | a>>(32-5)
    66  			b30 := b<<30 | b>>(32-30)
    67  			t := a5 + f + e + w[i&0xf] + _K2
    68  			a, b, c, d, e = t, a, b30, c, d
    69  		}
    70  		for ; i < 80; i++ {
    71  			tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
    72  			w[i&0xf] = tmp<<1 | tmp>>(32-1)
    73  			f := b ^ c ^ d
    74  			a5 := a<<5 | a>>(32-5)
    75  			b30 := b<<30 | b>>(32-30)
    76  			t := a5 + f + e + w[i&0xf] + _K3
    77  			a, b, c, d, e = t, a, b30, c, d
    78  		}
    79  
    80  		h0 += a
    81  		h1 += b
    82  		h2 += c
    83  		h3 += d
    84  		h4 += e
    85  
    86  		p = p[chunk:]
    87  	}
    88  
    89  	dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4] = h0, h1, h2, h3, h4
    90  }
    91  

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