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// Copyright 2017 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 algorithm
import (
"crypto/aes"
"crypto/cipher"
"crypto/des"
"golang.org/x/crypto/cast5"
)
// Cipher is an official symmetric key cipher algorithm. See RFC 4880,
// section 9.2.
type Cipher interface {
// Id returns the algorithm ID, as a byte, of the cipher.
Id() uint8
// KeySize returns the key size, in bytes, of the cipher.
KeySize() int
// BlockSize returns the block size, in bytes, of the cipher.
BlockSize() int
// New returns a fresh instance of the given cipher.
New(key []byte) cipher.Block
}
// The following constants mirror the OpenPGP standard (RFC 4880).
const (
TripleDES = CipherFunction(2)
CAST5 = CipherFunction(3)
AES128 = CipherFunction(7)
AES192 = CipherFunction(8)
AES256 = CipherFunction(9)
)
// CipherById represents the different block ciphers specified for OpenPGP. See
// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-13
var CipherById = map[uint8]Cipher{
TripleDES.Id(): TripleDES,
CAST5.Id(): CAST5,
AES128.Id(): AES128,
AES192.Id(): AES192,
AES256.Id(): AES256,
}
type CipherFunction uint8
// ID returns the algorithm Id, as a byte, of cipher.
func (sk CipherFunction) Id() uint8 {
return uint8(sk)
}
// KeySize returns the key size, in bytes, of cipher.
func (cipher CipherFunction) KeySize() int {
switch cipher {
case CAST5:
return cast5.KeySize
case AES128:
return 16
case AES192, TripleDES:
return 24
case AES256:
return 32
}
return 0
}
// BlockSize returns the block size, in bytes, of cipher.
func (cipher CipherFunction) BlockSize() int {
switch cipher {
case TripleDES:
return des.BlockSize
case CAST5:
return 8
case AES128, AES192, AES256:
return 16
}
return 0
}
// New returns a fresh instance of the given cipher.
func (cipher CipherFunction) New(key []byte) (block cipher.Block) {
var err error
switch cipher {
case TripleDES:
block, err = des.NewTripleDESCipher(key)
case CAST5:
block, err = cast5.NewCipher(key)
case AES128, AES192, AES256:
block, err = aes.NewCipher(key)
}
if err != nil {
panic(err.Error())
}
return
}
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