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Source file src/crypto/sha1/sha1block.go

Documentation: crypto/sha1

  // Copyright 2009 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package sha1
  
  const (
  	_K0 = 0x5A827999
  	_K1 = 0x6ED9EBA1
  	_K2 = 0x8F1BBCDC
  	_K3 = 0xCA62C1D6
  )
  
  // blockGeneric is a portable, pure Go version of the SHA-1 block step.
  // It's used by sha1block_generic.go and tests.
  func blockGeneric(dig *digest, p []byte) {
  	var w [16]uint32
  
  	h0, h1, h2, h3, h4 := dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4]
  	for len(p) >= chunk {
  		// Can interlace the computation of w with the
  		// rounds below if needed for speed.
  		for i := 0; i < 16; i++ {
  			j := i * 4
  			w[i] = uint32(p[j])<<24 | uint32(p[j+1])<<16 | uint32(p[j+2])<<8 | uint32(p[j+3])
  		}
  
  		a, b, c, d, e := h0, h1, h2, h3, h4
  
  		// Each of the four 20-iteration rounds
  		// differs only in the computation of f and
  		// the choice of K (_K0, _K1, etc).
  		i := 0
  		for ; i < 16; i++ {
  			f := b&c | (^b)&d
  			a5 := a<<5 | a>>(32-5)
  			b30 := b<<30 | b>>(32-30)
  			t := a5 + f + e + w[i&0xf] + _K0
  			a, b, c, d, e = t, a, b30, c, d
  		}
  		for ; i < 20; i++ {
  			tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
  			w[i&0xf] = tmp<<1 | tmp>>(32-1)
  
  			f := b&c | (^b)&d
  			a5 := a<<5 | a>>(32-5)
  			b30 := b<<30 | b>>(32-30)
  			t := a5 + f + e + w[i&0xf] + _K0
  			a, b, c, d, e = t, a, b30, c, d
  		}
  		for ; i < 40; i++ {
  			tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
  			w[i&0xf] = tmp<<1 | tmp>>(32-1)
  			f := b ^ c ^ d
  			a5 := a<<5 | a>>(32-5)
  			b30 := b<<30 | b>>(32-30)
  			t := a5 + f + e + w[i&0xf] + _K1
  			a, b, c, d, e = t, a, b30, c, d
  		}
  		for ; i < 60; i++ {
  			tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
  			w[i&0xf] = tmp<<1 | tmp>>(32-1)
  			f := ((b | c) & d) | (b & c)
  
  			a5 := a<<5 | a>>(32-5)
  			b30 := b<<30 | b>>(32-30)
  			t := a5 + f + e + w[i&0xf] + _K2
  			a, b, c, d, e = t, a, b30, c, d
  		}
  		for ; i < 80; i++ {
  			tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
  			w[i&0xf] = tmp<<1 | tmp>>(32-1)
  			f := b ^ c ^ d
  			a5 := a<<5 | a>>(32-5)
  			b30 := b<<30 | b>>(32-30)
  			t := a5 + f + e + w[i&0xf] + _K3
  			a, b, c, d, e = t, a, b30, c, d
  		}
  
  		h0 += a
  		h1 += b
  		h2 += c
  		h3 += d
  		h4 += e
  
  		p = p[chunk:]
  	}
  
  	dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4] = h0, h1, h2, h3, h4
  }
  

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