Data Encryption Standard - DES

DES

数据加密标准(Data Encryption Standard, DES)是一种对称密钥加密块密码算法,1976年被美国联邦政府的国家标准局确定为联邦资料处理标准(FIPS),随后在国际上广泛流传开来。它基于使用 56 位密钥的对称算法。这个算法因为包含一些机密设计元素,相对短的密钥长度以及怀疑内含美国国家安全局(NSA)的后门而在开始时有争议,DES 因此受到了强烈的学院派式的审查,并以此推动了现代的块密码及其密码分析的发展。

DES 现在已经不是一种安全的加密方法,主要因为它使用的 56 位密钥过短。1999 年 1 月,distributed.net 与电子前哨基金会合作,在 22 小时 15 分钟内即公开破解了一个 DES密钥。也有一些分析报告提出了该算法的理论上的弱点,虽然在实际中难以应用。为了提供实用所需的安全性,可以使用 DES 的派生算法 3DES 来进行加密,虽然 3DES 也存在理论上的攻击方法。在 2001 年,DES 作为一个标准已经被高级加密标准(AES)所取代。另外,DES 已经不再作为国家标准科技协会(前国家标准局)的一个标准。

算法描述

* 混淆和扩散

  1. 混淆(Confusion):是一种使密钥与密文之间的关系尽可能模糊的加密操作。如今实现混淆常用的一个元素就是替换,这个元素在 DES 和 AES 中都有使用。

  2. 扩散(Diffusion):是一种为了隐藏明文的统计属性而将一个明文符号的影响扩散到多个密文的加密操作。最简单的扩散元素就是位置换,它常用于 DES 中;而 AES 则使用更高级的 Mixcolumn 操作。

DES 是一种使用 56-bit 密钥对 64-bit 分组进行加密的密码。

DES 是一种对称密码,即其加密过程和解密过程使用相同的密钥,与几乎所有现代分组加密一样,DES 也是一种迭代算法。DES 对明文的每个分组的加密过程都包含 16 轮,且每轮的操作完全相同。每轮都会使用不同的子密钥,并且所有子密钥 kik_{i} 都从主密钥 kk 中推导而来。DES 的 Feistel 网络内部结构如下:

将 64-bit 的明文 x 进行初始按位置换 IP 后,此明文会被分成 L0L_{0}R0R_{0} 两部分;然后将得到的 32-bit 的左右两部分分别输入到 Feistel 网络,而 Feistel 网络包含 16 轮操作。右半部分 RiR_{i} 将被送入到函数 ff 中。ff 函数的输出将与 32-bit 的左半部分 LiL_{i} 进行 XOR。最后,左右两部分进行交换。后面的每轮都重复这个过程,可以表示为:

L_{i} = R_{i-1},$$$$R_{i} = L_{i-1} \oplus f(R_{i-1}, k_{i})

其中 i=1,2,..,16i=1,2,..,16, 经过 16 轮后,均为 32-bit 的左半部分 L16L_{16} 和右半部分 R16R_{16} 将再次交换,逆初始置换 IP1IP^{-1} 是 DES 的最后一步操作。逆初始置换 IP1IP^{-1} 是初始置换 IPIP 的逆操作。每轮中的轮密钥 kik_{i} 均来自于 56-bit 的主密钥,而这个过程则是通过**密钥编排[Key schedule]**实现的。

初始置换和逆初始置换

IPIP 在第一轮迭代之前进行,目的是将原明文块的位进行换位操作(查表)。

IP1IP^{-1} 在最后一轮迭代之后进行,在加密算法中输出为密文,在解密算法中输出明文。

# 初始置换 IP
IP = [58, 50, 42, 34, 26, 18, 10, 2,
      60, 52, 44, 36, 28, 20, 12, 4,
      62, 54, 46, 38, 30, 22, 14, 6,
      64, 56, 48, 40, 32, 24, 16, 8,
      57, 49, 41, 33, 25, 17, 9, 1,
      59, 51, 43, 35, 27, 19, 11, 3,
      61, 53, 45, 37, 29, 21, 13, 5,
      63, 55, 47, 39, 31, 23, 15, 7]

# 逆初始置换 PI
PI = [40, 8, 48, 16, 56, 24, 64, 32,
    39, 7, 47, 15, 55, 23, 63, 31,
    38, 6, 46, 14, 54, 22, 62, 30,
    37, 5, 45, 13, 53, 21, 61, 29,
    36, 4, 44, 12, 52, 20, 60, 28,
    35, 3, 43, 11, 51, 19, 59, 27,
    34, 2, 42, 10, 50, 18, 58, 26,
    33, 1, 41, 9, 49, 17, 57, 25]

# 初始置换 IP / 逆初始置换 PI
def permut(self, block, table):
    return [block[x-1] for x in table]

ff 函数

ff 函数在 DES 的安全性中扮演着重要的角色,在第 ii 轮中,ff 函数的输入为前一轮输出的右半部分 Li1L_{i-1} 和当地前轮密钥 kik_{i}ff 函数的输出将用作 XORXOR-掩码,用来加密左半部分输入 Li1L_{i-1}ff 函数的结构如下图所示:

E-盒拓展置换

首先将输入分为 8 个 4 位的分组,然后把每个分组拓展为 6 位,从而将 32 位的输入拓展为 48 位。这个过程在 E-盒 中进行,E-盒 是一个特殊的置换,第一个分组包含的位为 (1,2,3,4)(1, 2, 3, 4),第二个分组包含的位为 (5,6,7,8)(5, 6, 7, 8), 以此类推。

# 拓展置换 E / E-盒 / 扩散
# 32-bit -> 8 * 4-bit -> 8 * 6-bit -> 48-bit
E = [32, 1, 2, 3, 4, 5,
     4, 5, 6, 7, 8, 9,
     8, 9, 10, 11, 12, 13,
     12, 13, 14, 15, 16, 17,
     16, 17, 18, 19, 20, 21,
     20, 21, 22, 23, 24, 25,
     24, 25, 26, 27, 28, 29,
     28, 29, 30, 31, 32, 1]

拓展盒增加了 DES 的扩散行为,因为某些输入位会影响两个不同的输出位置。

S-盒混淆替换

接着将 E-盒 拓展得到的 48 位的结果与轮密钥 kik_{i} 进行 XOR 操作,并将 8 个 6 位长的分组送到 8 个不同的替换盒中——这个替换盒也称为 S-盒,每个 S-盒 都是一个查找表,它将 6 位的输入映射为 4 位的输出。

每个 6 为的输入位的最重要的位 MSB 和最不重要位 LSB 将选择表行,而 4 个内部位,则选择列。

从密码学的角度来讲,S-盒 是 DES 的核心,也是该算法中唯一的非线性元素,并提供了混淆

# S-盒 / 混淆
S_BOX = [        
[[14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7],
 [0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8],
 [4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0],
 [15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13],
],
[[15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10],
 [3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5],
 [0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15],
 [13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9],
],
[[10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8],
 [13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1],
 [13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7],
 [1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12],
],
[[7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15],
 [13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9],
 [10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4],
 [3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14],
],  
[[2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9],
 [14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6],
 [4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14],
 [11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3],
], 
[[12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11],
 [10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8],
 [9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6],
 [4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13],
], 
[[4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1],
 [13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6],
 [1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2],
 [6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12],
], 
[[13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7],
 [1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2],
 [7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8],
 [2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11],
]
]

p 置换

ff 函数中每轮 S-盒 替换后的简单置换操作。

# f 函数中每轮 S-盒 替换后的置换操作
P = [16, 7, 20, 21, 29, 12, 28, 17,
    1, 15, 23, 26, 5, 18, 31, 10,
    2, 8, 24, 14, 32, 27, 3, 9,
    19, 13, 30, 6, 22, 11, 4, 25]

密钥编排

密钥编排从原始的 56 位密钥中得到 16 个轮密钥 kik_{i} ,其中每个轮密钥 kik_{i} 都是 48 位。轮密钥的另一个术语叫 子密钥。

# 初始密钥置换 PC-1 / 64-bits -> 56-bits
PC_1 = [57, 49, 41, 33, 25, 17, 9,
        1, 58, 50, 42, 34, 26, 18,
        10, 2, 59, 51, 43, 35, 27,
        19, 11, 3, 60, 52, 44, 36,
        63, 55, 47, 39, 31, 23, 15,
        7, 62, 54, 46, 38, 30, 22,
        14, 6, 61, 53, 45, 37, 29,
        21, 13, 5, 28, 20, 12, 4]
# 轮密钥置换 PC-2 / 返回 key_i
PC_2 = [14, 17, 11, 24, 1, 5, 3, 28,
        15, 6, 21, 10, 23, 19, 12, 4,
        26, 8, 16, 7, 27, 20, 13, 2,
        41, 52, 31, 37, 47, 55, 30, 40,
        51, 45, 33, 48, 44, 49, 39, 56,
        34, 53, 46, 42, 50, 36, 29, 32]

完整代码:

#-*- coding: utf8 -*-
# Hill Cipher By 3ND

from base64 import b64encode

ENC, DEC = 1, 0

# 初始置换 IP
IP = [58, 50, 42, 34, 26, 18, 10, 2,
      60, 52, 44, 36, 28, 20, 12, 4,
      62, 54, 46, 38, 30, 22, 14, 6,
      64, 56, 48, 40, 32, 24, 16, 8,
      57, 49, 41, 33, 25, 17, 9, 1,
      59, 51, 43, 35, 27, 19, 11, 3,
      61, 53, 45, 37, 29, 21, 13, 5,
      63, 55, 47, 39, 31, 23, 15, 7]

# 逆初始置换 PI
PI = [40, 8, 48, 16, 56, 24, 64, 32,
    39, 7, 47, 15, 55, 23, 63, 31,
    38, 6, 46, 14, 54, 22, 62, 30,
    37, 5, 45, 13, 53, 21, 61, 29,
    36, 4, 44, 12, 52, 20, 60, 28,
    35, 3, 43, 11, 51, 19, 59, 27,
    34, 2, 42, 10, 50, 18, 58, 26,
    33, 1, 41, 9, 49, 17, 57, 25]

# 拓展置换 E / E-盒 / 扩散
# 32-bit -> 8 * 4-bit -> 8 * 6-bit -> 48-bit
E = [32, 1, 2, 3, 4, 5,
     4, 5, 6, 7, 8, 9,
     8, 9, 10, 11, 12, 13,
     12, 13, 14, 15, 16, 17,
     16, 17, 18, 19, 20, 21,
     20, 21, 22, 23, 24, 25,
     24, 25, 26, 27, 28, 29,
     28, 29, 30, 31, 32, 1]

# 初始密钥置换 PC-1 / 64-bits -> 56-bits
PC_1 = [57, 49, 41, 33, 25, 17, 9,
        1, 58, 50, 42, 34, 26, 18,
        10, 2, 59, 51, 43, 35, 27,
        19, 11, 3, 60, 52, 44, 36,
        63, 55, 47, 39, 31, 23, 15,
        7, 62, 54, 46, 38, 30, 22,
        14, 6, 61, 53, 45, 37, 29,
        21, 13, 5, 28, 20, 12, 4]

# 密钥左移位数
SHIFT = [1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1]

# 轮密钥置换 PC-2 / 返回 key_i
PC_2 = [14, 17, 11, 24, 1, 5, 3, 28,
        15, 6, 21, 10, 23, 19, 12, 4,
        26, 8, 16, 7, 27, 20, 13, 2,
        41, 52, 31, 37, 47, 55, 30, 40,
        51, 45, 33, 48, 44, 49, 39, 56,
        34, 53, 46, 42, 50, 36, 29, 32]

# S-盒 / 混淆
S_BOX = [        
[[14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7],
 [0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8],
 [4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0],
 [15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13],
],
[[15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10],
 [3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5],
 [0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15],
 [13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9],
],
[[10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8],
 [13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1],
 [13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7],
 [1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12],
],
[[7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15],
 [13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9],
 [10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4],
 [3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14],
],  
[[2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9],
 [14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6],
 [4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14],
 [11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3],
], 
[[12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11],
 [10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8],
 [9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6],
 [4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13],
], 
[[4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1],
 [13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6],
 [1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2],
 [6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12],
], 
[[13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7],
 [1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2],
 [7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8],
 [2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11],
]
]

# f 函数中每轮 S-盒 替换后的置换操作
P = [16, 7, 20, 21, 29, 12, 28, 17,
    1, 15, 23, 26, 5, 18, 31, 10,
    2, 8, 24, 14, 32, 27, 3, 9,
    19, 13, 30, 6, 22, 11, 4, 25]

# 分割列表 s 为 n 个子列表
def nsplit(s, n):
    return [s[k:k + n] for k in range(0, len(s), n)]

# 转化给定的字符串转换为特定大小的二进制值
def binvalue(val, bitsize):
    binval = bin(val)[2:] if isinstance(val, int) else bin(ord(val))[2:]
    if len(binval) > bitsize:
        raise "[?]Exception:二进制值超出预期大小({})".format(binval)
    while len(binval) < bitsize:
        binval = "0" + binval # 填充 0 
    return binval

# 字符串/数组转化为二进制数组
def str2bin(text):
    array = list()
    for char in text:
        # 1-byte -> 8-bits
        binval = binvalue(char, 8)
        # 逐位加入返回数组
        array.extend([int(x) for x in list(binval)])
    return array

# 二进制数组转化为字符串
def bin2str(array):
    # 二进制数组 8-bits -> 1-byte, 转化为字符串返回
    res = ''.join([chr(int(y,2)) for y in [''.join([str(x) for x in _bytes]) for _bytes in  nsplit(array,8)]])   
    return res

class DES():
    # 初始化函数 __init__()
    def __init__(self):
        self.key = None
        self.text = None
        self.keys = list()
    
    # 初始置换 IP / 逆初始置换 PI
    def permut(self, block, table):
        return [block[x-1] for x in table]

    # 拓展置换 E / 扩散
    def expand(self, block, table):
        return [block[x-1] for x in table]
    
    # S-盒置换 / 混淆
    def sbox_substitute(self, R_e):
        subblocks = nsplit(R_e, 6) # 48-bits -> 8 * 6-bits
        result = list()
        for i in range(len(subblocks)):
            block = subblocks[i]
            # MSB block[0] + LSB block[5] -> 行号(Binary)
            row = int(str(block[0]) + str(block[5]), 2)
            # block[2, 3, 4, 5] -> 列号(Binary)
            column = int(''.join([str(x) for x in block[1:-1]]), 2)
            # 第 i 轮 S-盒 的置换值 val
            val = S_BOX[i][row][column]
            # 6-bits -> 4-bits
            bin = binvalue(val, 4)
            # 加入返回列表
            result += [int(x) for x in bin]
        return result

    # 密钥编排 / 密钥生成
    def generatekeys(self):
        self.keys = []
        key = str2bin(self.key)
        # PC-1 置换
        key = self.permut(key, PC_1)
        # 56-bits -> 2 * 28-bits
        L, R = nsplit(key, 28)
        for i in range(16):
            # 每轮的密钥移位
            L, R = self.shift(L, R, SHIFT[i])
            # 合并 Left / Right 
            overall = L + R
            # 变换完成后存储 Key_i
            self.keys.append(self.permut(overall, PC_2))

    # 异或运算 - 列表
    def xor(self, l1, l2):
        return [x ^ y for x, y in zip(l1, l2)]

    # 密匙编排中的移位运算
    def shift(self, L, R, n):
        return L[n:] + L[:n], R[n:] + R[:n]
    
    # PKCS5 模式填充
    def addPadding(self):
        pad_len = 8 - (len(self.text) % 8)
        self.text += pad_len * chr(pad_len)
    
    # 去除填充的明文文本
    def removePadding(self, data):
        pad_len = ord(data[-1])
        return data[:-pad_len]
    
    # 加密
    def encrypt(self, key, text, padding=False):
        return self.calc(key, text, ENC, padding)
    
    # 解密
    def decrypt(self, key, text, padding=False):
        return self.calc(key, text, DEC, padding)

    # 执行加密和解密
    def calc(self, key, text, action=ENC, padding=False):
        if len(key) < 8:
            raise "[?]Exception:密钥长度需要为 8-bits"
        # 密钥长度 > 8 则截断多余部分
        elif len(key) > 8:
            key = key[:8]
        # 初始化参数
        self.key = key
        self.text = text
        # 是否进行文本填充
        if padding and action == ENC:
            self.addPadding()
        # 未进行填充操作,则指定的数据大小必须为 n * 8-bits
        elif len(self.text) % 8 != 0:#
            raise "[?]Exception:密钥大小不是 n * 8-bits"
        # 生成密钥
        self.generatekeys()
        # 将待加密和解密的文本转化为 8-bytes -> 64-bits
        text_blocks = nsplit(self.text, 8)
        result = list()
        for block in text_blocks:
            block = str2bin(block)
            # 初始置换 IP()
            block = self.permut(block, IP)
            # 64-bits -> L 32-bits + R 32-bits
            L, R = nsplit(block, 32)
            tmp = None
            # Feistel 中的 16 轮运算
            for i in range(16):
                # 右半部分进行拓展置换 E 进行扩散
                # 32-bits -> 48-bits 用于与 Key_i 结合
                R_e = self.expand(R, E)
                # 异或运算
                if action == ENC: # 加密操作从前往后选择密钥
                    tmp = self.xor(self.keys[i], R_e)
                else: # 如果是解密则从后往前选择 Key
                    tmp = self.xor(self.keys[15-i], R_e)
                # f函数中 S-盒替换 进行混淆
                tmp = self.sbox_substitute(tmp)
                # f 函数中的 P 置换
                tmp = self.permut(tmp, P)
                # 左半部分 L 与 f 函数的输出进行异或运算
                tmp = self.xor(L, tmp)
                # 左右两部分进行置换
                L = R
                R = tmp
            # 最后进行初始 IP 置换的 逆置换
            result += self.permut(R + L, PI)
        # 二进制转化为字符串
        final_res = bin2str(result)
        # 填充数据的处理
        if padding and action == DEC: # 解密操作获取的明文去除填充数据
            return self.removePadding(final_res) 
        else: # 返回最后的结果(解密->明文,加密->密文)
            return final_res 
    
if __name__ == '__main__':
    Key = raw_input("Please Input Key >> ")
    #Key = "[email protected]"
    Plain = raw_input("Please Input Plain >> ")
    #Plain = "NiceDES!"
    C = DES()
    Cipher = C.encrypt(Key, Plain, padding=True)
    Plian_Dec = C.decrypt(Key, Cipher, padding=True)
    print "Key: %s" % Key[:8]
    print "Plain Text: %s" % Plain
    print "Ciphered Text: %s" % b64encode(Cipher)
    print "Deciphered: %s" % Plian_Dec

运行测试: