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cipher.go
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// 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 (
"crypto/cipher"
"crypto/internal/fips140/alias"
"crypto/internal/fips140only"
"errors"
"internal/byteorder"
"strconv"
)
// The DES block size in bytes.
const BlockSize = 8
type KeySizeError int
func (k KeySizeError) Error() string {
return "crypto/des: invalid key size " + strconv.Itoa(int(k))
}
// desCipher is an instance of DES encryption.
type desCipher struct {
subkeys [16]uint64
}
// NewCipher creates and returns a new [cipher.Block].
func NewCipher(key []byte) (cipher.Block, error) {
if fips140only.Enabled {
return nil, errors.New("crypto/des: use of DES is not allowed in FIPS 140-only mode")
}
if len(key) != 8 {
return nil, KeySizeError(len(key))
}
c := new(desCipher)
c.generateSubkeys(key)
return c, nil
}
func (c *desCipher) BlockSize() int { return BlockSize }
func (c *desCipher) Encrypt(dst, src []byte) {
if len(src) < BlockSize {
panic("crypto/des: input not full block")
}
if len(dst) < BlockSize {
panic("crypto/des: output not full block")
}
if alias.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
panic("crypto/des: invalid buffer overlap")
}
cryptBlock(c.subkeys[:], dst, src, false)
}
func (c *desCipher) Decrypt(dst, src []byte) {
if len(src) < BlockSize {
panic("crypto/des: input not full block")
}
if len(dst) < BlockSize {
panic("crypto/des: output not full block")
}
if alias.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
panic("crypto/des: invalid buffer overlap")
}
cryptBlock(c.subkeys[:], dst, src, true)
}
// A tripleDESCipher is an instance of TripleDES encryption.
type tripleDESCipher struct {
cipher1, cipher2, cipher3 desCipher
}
// NewTripleDESCipher creates and returns a new [cipher.Block].
func NewTripleDESCipher(key []byte) (cipher.Block, error) {
if fips140only.Enabled {
return nil, errors.New("crypto/des: use of TripleDES is not allowed in FIPS 140-only mode")
}
if len(key) != 24 {
return nil, KeySizeError(len(key))
}
c := new(tripleDESCipher)
c.cipher1.generateSubkeys(key[:8])
c.cipher2.generateSubkeys(key[8:16])
c.cipher3.generateSubkeys(key[16:])
return c, nil
}
func (c *tripleDESCipher) BlockSize() int { return BlockSize }
func (c *tripleDESCipher) Encrypt(dst, src []byte) {
if len(src) < BlockSize {
panic("crypto/des: input not full block")
}
if len(dst) < BlockSize {
panic("crypto/des: output not full block")
}
if alias.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
panic("crypto/des: invalid buffer overlap")
}
b := byteorder.BEUint64(src)
b = permuteInitialBlock(b)
left, right := uint32(b>>32), uint32(b)
left = (left << 1) | (left >> 31)
right = (right << 1) | (right >> 31)
for i := 0; i < 8; i++ {
left, right = feistel(left, right, c.cipher1.subkeys[2*i], c.cipher1.subkeys[2*i+1])
}
for i := 0; i < 8; i++ {
right, left = feistel(right, left, c.cipher2.subkeys[15-2*i], c.cipher2.subkeys[15-(2*i+1)])
}
for i := 0; i < 8; i++ {
left, right = feistel(left, right, c.cipher3.subkeys[2*i], c.cipher3.subkeys[2*i+1])
}
left = (left << 31) | (left >> 1)
right = (right << 31) | (right >> 1)
preOutput := (uint64(right) << 32) | uint64(left)
byteorder.BEPutUint64(dst, permuteFinalBlock(preOutput))
}
func (c *tripleDESCipher) Decrypt(dst, src []byte) {
if len(src) < BlockSize {
panic("crypto/des: input not full block")
}
if len(dst) < BlockSize {
panic("crypto/des: output not full block")
}
if alias.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
panic("crypto/des: invalid buffer overlap")
}
b := byteorder.BEUint64(src)
b = permuteInitialBlock(b)
left, right := uint32(b>>32), uint32(b)
left = (left << 1) | (left >> 31)
right = (right << 1) | (right >> 31)
for i := 0; i < 8; i++ {
left, right = feistel(left, right, c.cipher3.subkeys[15-2*i], c.cipher3.subkeys[15-(2*i+1)])
}
for i := 0; i < 8; i++ {
right, left = feistel(right, left, c.cipher2.subkeys[2*i], c.cipher2.subkeys[2*i+1])
}
for i := 0; i < 8; i++ {
left, right = feistel(left, right, c.cipher1.subkeys[15-2*i], c.cipher1.subkeys[15-(2*i+1)])
}
left = (left << 31) | (left >> 1)
right = (right << 31) | (right >> 1)
preOutput := (uint64(right) << 32) | uint64(left)
byteorder.BEPutUint64(dst, permuteFinalBlock(preOutput))
}