1 files changed, 98 insertions, 0 deletions
diff --git a/libgo/go/crypto/des/block.go b/libgo/go/crypto/des/block.go
new file mode 100644
index 00000000000..e18eaedf580
--- /dev/null
+++ b/libgo/go/crypto/des/block.go
@@ -0,0 +1,98 @@
+// 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 = permuteBlock(b, initialPermutation[:])
+	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, permuteBlock(preOutput, finalPermutation[:]))
+}
+
+// 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 ^ permuteBlock(uint64(right), expansionFunction[:])
+	var sBoxResult uint32
+	for i := uint8(0); i < 8; i++ {
+		sBoxLocation := uint8(sBoxLocations>>42) & 0x3f
+		sBoxLocations <<= 6
+		// row determined by 1st and 6th bit
+		row := (sBoxLocation & 0x1) | ((sBoxLocation & 0x20) >> 4)
+		// column is middle four bits
+		column := (sBoxLocation >> 1) & 0xf
+		sBoxResult |= uint32(sBoxes[i][row][column]) << (4 * (7 - i))
+	}
+	return uint32(permuteBlock(uint64(sBoxResult), permutationFunction[:]))
+}
+
+// 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
+}
+
+// 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 *Cipher) 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[:])
+	}
+}