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  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] = tmp<<1 | tmp>>(32-1)
		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] = tmp<<1 | tmp>>(32-1)
		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] = tmp<<1 | tmp>>(32-1)
		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] = tmp<<1 | tmp>>(32-1)
		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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