1 files changed, 223 insertions, 0 deletions
diff --git a/src/crypto/des/block.go b/src/crypto/des/block.go
new file mode 100644
index 000000000..26355a22e
--- /dev/null
+++ b/src/crypto/des/block.go
@@ -0,0 +1,223 @@
+// Copyright 2011 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 des
+
+import (
+	"encoding/binary"
+)
+
+func cryptBlock(subkeys []uint64, dst, src []byte, decrypt bool) {
+	b := binary.BigEndian.Uint64(src)
+	b = permuteInitialBlock(b)
+	left, right := uint32(b>>32), uint32(b)
+
+	var subkey uint64
+	for i := 0; i < 16; i++ {
+		if decrypt {
+			subkey = subkeys[15-i]
+		} else {
+			subkey = subkeys[i]
+		}
+
+		left, right = right, left^feistel(right, subkey)
+	}
+	// switch left & right and perform final permutation
+	preOutput := (uint64(right) << 32) | uint64(left)
+	binary.BigEndian.PutUint64(dst, permuteFinalBlock(preOutput))
+}
+
+// Encrypt one block from src into dst, using the subkeys.
+func encryptBlock(subkeys []uint64, dst, src []byte) {
+	cryptBlock(subkeys, dst, src, false)
+}
+
+// Decrypt one block from src into dst, using the subkeys.
+func decryptBlock(subkeys []uint64, dst, src []byte) {
+	cryptBlock(subkeys, dst, src, true)
+}
+
+// DES Feistel function
+func feistel(right uint32, key uint64) (result uint32) {
+	sBoxLocations := key ^ expandBlock(right)
+	var sBoxResult uint32
+	for i := uint8(0); i < 8; i++ {
+		sBoxLocation := uint8(sBoxLocations>>42) & 0x3f
+		sBoxLocations <<= 6
+		// row determined by 1st and 6th bit
+		// column is middle four bits
+		row := (sBoxLocation & 0x1) | ((sBoxLocation & 0x20) >> 4)
+		column := (sBoxLocation >> 1) & 0xf
+		sBoxResult ^= feistelBox[i][16*row+column]
+	}
+	return sBoxResult
+}
+
+// feistelBox[s][16*i+j] contains the output of permutationFunction
+// for sBoxes[s][i][j] << 4*(7-s)
+var feistelBox [8][64]uint32
+
+// general purpose function to perform DES block permutations
+func permuteBlock(src uint64, permutation []uint8) (block uint64) {
+	for position, n := range permutation {
+		bit := (src >> n) & 1
+		block |= bit << uint((len(permutation)-1)-position)
+	}
+	return
+}
+
+func init() {
+	for s := range sBoxes {
+		for i := 0; i < 4; i++ {
+			for j := 0; j < 16; j++ {
+				f := uint64(sBoxes[s][i][j]) << (4 * (7 - uint(s)))
+				f = permuteBlock(uint64(f), permutationFunction[:])
+				feistelBox[s][16*i+j] = uint32(f)
+			}
+		}
+	}
+}
+
+// expandBlock expands an input block of 32 bits,
+// producing an output block of 48 bits.
+func expandBlock(src uint32) (block uint64) {
+	// rotate the 5 highest bits to the right.
+	src = (src << 5) | (src >> 27)
+	for i := 0; i < 8; i++ {
+		block <<= 6
+		// take the 6 bits on the right
+		block |= uint64(src) & (1<<6 - 1)
+		// advance by 4 bits.
+		src = (src << 4) | (src >> 28)
+	}
+	return
+}
+
+// permuteInitialBlock is equivalent to the permutation defined
+// by initialPermutation.
+func permuteInitialBlock(block uint64) uint64 {
+	// block = b7 b6 b5 b4 b3 b2 b1 b0 (8 bytes)
+	b1 := block >> 48
+	b2 := block << 48
+	block ^= b1 ^ b2 ^ b1<<48 ^ b2>>48
+
+	// block = b1 b0 b5 b4 b3 b2 b7 b6
+	b1 = block >> 32 & 0xff00ff
+	b2 = (block & 0xff00ff00)
+	block ^= b1<<32 ^ b2 ^ b1<<8 ^ b2<<24 // exchange b0 b4 with b3 b7
+
+	// block is now b1 b3 b5 b7 b0 b2 b4 b7, the permutation:
+	//                  ...  8
+	//                  ... 24
+	//                  ... 40
+	//                  ... 56
+	//  7  6  5  4  3  2  1  0
+	// 23 22 21 20 19 18 17 16
+	//                  ... 32
+	//                  ... 48
+
+	// exchange 4,5,6,7 with 32,33,34,35 etc.
+	b1 = block & 0x0f0f00000f0f0000
+	b2 = block & 0x0000f0f00000f0f0
+	block ^= b1 ^ b2 ^ b1>>12 ^ b2<<12
+
+	// block is the permutation:
+	//
+	//   [+8]         [+40]
+	//
+	//  7  6  5  4
+	// 23 22 21 20
+	//  3  2  1  0
+	// 19 18 17 16    [+32]
+
+	// exchange 0,1,4,5 with 18,19,22,23
+	b1 = block & 0x3300330033003300
+	b2 = block & 0x00cc00cc00cc00cc
+	block ^= b1 ^ b2 ^ b1>>6 ^ b2<<6
+
+	// block is the permutation:
+	// 15 14
+	// 13 12
+	// 11 10
+	//  9  8
+	//  7  6
+	//  5  4
+	//  3  2
+	//  1  0 [+16] [+32] [+64]
+
+	// exchange 0,2,4,6 with 9,11,13,15:
+	b1 = block & 0xaaaaaaaa55555555
+	block ^= b1 ^ b1>>33 ^ b1<<33
+
+	// block is the permutation:
+	// 6 14 22 30 38 46 54 62
+	// 4 12 20 28 36 44 52 60
+	// 2 10 18 26 34 42 50 58
+	// 0  8 16 24 32 40 48 56
+	// 7 15 23 31 39 47 55 63
+	// 5 13 21 29 37 45 53 61
+	// 3 11 19 27 35 43 51 59
+	// 1  9 17 25 33 41 49 57
+	return block
+}
+
+// permuteInitialBlock is equivalent to the permutation defined
+// by finalPermutation.
+func permuteFinalBlock(block uint64) uint64 {
+	// Perform the same bit exchanges as permuteInitialBlock
+	// but in reverse order.
+	b1 := block & 0xaaaaaaaa55555555
+	block ^= b1 ^ b1>>33 ^ b1<<33
+
+	b1 = block & 0x3300330033003300
+	b2 := block & 0x00cc00cc00cc00cc
+	block ^= b1 ^ b2 ^ b1>>6 ^ b2<<6
+
+	b1 = block & 0x0f0f00000f0f0000
+	b2 = block & 0x0000f0f00000f0f0
+	block ^= b1 ^ b2 ^ b1>>12 ^ b2<<12
+
+	b1 = block >> 32 & 0xff00ff
+	b2 = (block & 0xff00ff00)
+	block ^= b1<<32 ^ b2 ^ b1<<8 ^ b2<<24
+
+	b1 = block >> 48
+	b2 = block << 48
+	block ^= b1 ^ b2 ^ b1<<48 ^ b2>>48
+	return block
+}
+
+// creates 16 28-bit blocks rotated according
+// to the rotation schedule
+func ksRotate(in uint32) (out []uint32) {
+	out = make([]uint32, 16)
+	last := in
+	for i := 0; i < 16; i++ {
+		// 28-bit circular left shift
+		left := (last << (4 + ksRotations[i])) >> 4
+		right := (last << 4) >> (32 - ksRotations[i])
+		out[i] = left | right
+		last = out[i]
+	}
+	return
+}
+
+// creates 16 56-bit subkeys from the original key
+func (c *desCipher) generateSubkeys(keyBytes []byte) {
+	// apply PC1 permutation to key
+	key := binary.BigEndian.Uint64(keyBytes)
+	permutedKey := permuteBlock(key, permutedChoice1[:])
+
+	// rotate halves of permuted key according to the rotation schedule
+	leftRotations := ksRotate(uint32(permutedKey >> 28))
+	rightRotations := ksRotate(uint32(permutedKey<<4) >> 4)
+
+	// generate subkeys
+	for i := 0; i < 16; i++ {
+		// combine halves to form 56-bit input to PC2
+		pc2Input := uint64(leftRotations[i])<<28 | uint64(rightRotations[i])
+		// apply PC2 permutation to 7 byte input
+		c.subkeys[i] = permuteBlock(pc2Input, permutedChoice2[:])
+	}
+}