一、算法介紹

1.1 背景

DES 算法是由美國(guó) IBM 公司在 20 世紀(jì) 70 年代提出，并被美國(guó)政府、美國(guó)國(guó)家標(biāo)準(zhǔn)局和美國(guó)國(guó)家標(biāo)準(zhǔn)協(xié)會(huì)采納和承認(rèn)的一種標(biāo)準(zhǔn)加密算法。

它屬于分組加密算法，即在明文加密和密文解密過程中，信息都是按照固定長(zhǎng)度分組后進(jìn)行處理的。混淆和擴(kuò)散是它采用的兩個(gè)最重要的安全特性。

混淆是指通過密碼算法使明文和密文以及密鑰的關(guān)系非常復(fù)雜，無法從數(shù)學(xué)上描述或者統(tǒng)計(jì)。擴(kuò)散是指明文和密鑰中每一位信息的變動(dòng)，都會(huì)影響到密文中許多位信息的變動(dòng)，從而隱藏統(tǒng)計(jì)上的特性，增加密碼的安全。

1.2 原理

DES 算法將明文分成 64 位大小的眾多數(shù)據(jù)塊，即分組長(zhǎng)度為 64 位，同時(shí)用 64 位密鑰（有效密鑰 56 位）對(duì) 64 位明文信息加密，最終形成 64 位的密文。如果明文長(zhǎng)度不足 64 位，則將其擴(kuò)展為 64 位（如補(bǔ)零等方法）。

具體加密過程，首先是將輸入的數(shù)據(jù)進(jìn)行初始換位（$IP$），即將明文 $M$ 中數(shù)據(jù)的排列順序按一定的規(guī)則重新排列，生成新的數(shù)據(jù)序列，以打亂原來的次序。然后將變換后的數(shù)據(jù)平分成左右兩部分，左邊記為 $L_0$，右邊記為 $R_0$，然后對(duì) $R_0$ 實(shí)行在子密鑰（由加密密鑰產(chǎn)生）控制下的變換 $f$，結(jié)果記為$f(R_0,K_1)$，再與 $L_0$ 做逐位異或運(yùn)算，其結(jié)果記為 $R_1$，$R_0$ 則作為下一輪的 $L_1$。如此循環(huán) 16 輪，最后得到 $L_{16}$、$R_{16}$。再對(duì) $L_{16}$、$R_{16}$ 實(shí)行逆初始置換 $I{P}^{?1}$，即可得到加密數(shù)據(jù)。
解密過程與此類似，不同之處僅在于子密鑰的使用順序正好相反。

DES 全部 16 輪的加密過程如圖所示：

1.3 基本功能函數(shù)

1.3.1 初始置換函數(shù) $IP$

它的作用是把輸入的 64 位數(shù)據(jù)塊的排列順序打亂，每位數(shù)據(jù)按照下面換位規(guī)則重新組合；即將第 58 位換到第 1 位，第 50 位換到第 2 位，……，依次類推；重組后的 64 位輸出分為 $L_0$、$R_0$（左、右）兩部分，每部分分別為 32 位。初始置換如表如下所示：

$R_0$ 和 $K_1$ 經(jīng)過 變換后的輸出結(jié)果，再和 $L_0$進(jìn)行異或運(yùn)算，輸出結(jié)果做為 $R_1$，$R_0$ 則賦給 $L_1$。$L_1$ 和 $R_1$ 同樣再做類似運(yùn)算生成$L_2$ 和 $R_2$，……，經(jīng)過 16次運(yùn)算后生成$L_{16}$ 的 $R_{16}$。

1.3.2 $f$ 輪函數(shù)

$f$ 輪函數(shù)是多個(gè)置換函數(shù)和替代函數(shù)的組合函數(shù)，它將 32 位比特的輸入變換為 32 位的輸出；$R_i$ 經(jīng)過擴(kuò)展運(yùn)算 $E$ 變換后擴(kuò)展為 48 位的$E(R_i)$ ，與 $K_{i+1}$ 進(jìn)行異或運(yùn)算后輸出的結(jié)果分成 8 組，每組 6 比特的并聯(lián) $B$，$B$=$B_1$$B_2$$B_3$$B_4$$B_5$$B_6$$B_7$$B_8$，再經(jīng)過 8 個(gè) $S$ 盒的選擇壓縮運(yùn)算轉(zhuǎn)換為 4 位，8 個(gè) 4 位合并為 32 位后再經(jīng)過 $P$ 變換輸出為 32 位的$f(R_i,K_{i+1})$ 。其中，擴(kuò)展運(yùn)算 $E$ 與置換 $P$ 主要作用是增加算法的擴(kuò)展效果。

$f$ 輪函數(shù)處理流程如下圖所示：

1.3.3 逆初始置換函數(shù) $I{P}^{?1}$

它將 $L_{16}$ 和 $R_{16}$ 作為輸入，進(jìn)行逆初始換位得到密文輸出。逆初始換位是初始位的逆運(yùn)算，逆初始置換的換位規(guī)則如下表所示：

1.4 子密鑰的生成

具體子密鑰的產(chǎn)生流程如圖所示：

輸入的初始密鑰值為 64 位；但 DES 算法規(guī)定，64 位初始密鑰中第 8、16、……、64 位是奇偶檢驗(yàn)位，不參與 DES 運(yùn)算。所以，實(shí)際可用位數(shù)只有56 位，經(jīng)過縮小選擇換位表即置換選擇 $PC1$ 的變換后，初始密鑰的位數(shù)由 64 位變成了 56 位，將其平分為兩部分 $C_0$（28 位）、$D_0$（28 位）。然后，分別進(jìn)行第 1 次循環(huán)左移，得到 $C_1$、$D_1$，需要注意的是，循環(huán)左移需經(jīng)過 16 輪次，第 $i$ 輪迭代時(shí)對(duì)應(yīng)的左移位數(shù)要依據(jù)移位表的規(guī)則進(jìn)行。接著，將 $C_1$、 $D_1$ 合并后得到 56 位的輸出結(jié)果，再經(jīng)過縮小選擇換位表即置換選擇 $PC2$ ，從而得到了密鑰 $K_1$（48 位），依次類推，便可得到 $K_2$、……、$K_{16}$。

二、代碼實(shí)現(xiàn)

2.1 子密鑰生成實(shí)現(xiàn)

# ========================================
# 一、子密鑰生成
# (1) 初始置換 64->56
# 64位的種子密鑰經(jīng)過PC_1置換后，生成56位的密鑰
# (2) 劃分 56->(28,28)
# 經(jīng)過初始置換后的56位密鑰被均分成C0和D0兩部分
# (3) 循環(huán)左移
# 第一輪，C0和D0根據(jù)移位次數(shù)表各自進(jìn)行循環(huán)左移
# 得到C1和D1
# 每一輪的C和D值是由上一輪的C和D值循環(huán)左移得到的
# (4) 合并 (28,28)->56->48
# 左移后的兩部分再次合并,通過一個(gè)選擇壓縮表(PC_2)
# 得到這一輪的子密鑰
# (5)重復(fù)3、4操作,最終得到16個(gè)子密鑰
# ========================================# 置換選擇表1(PC_1) 64->56
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]# 選擇壓縮表2(PC_2) 56->48
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]# 移位次數(shù)表
shift_num = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1]def pc_1_change(bin_key):"""初始置換64位的種子密鑰經(jīng)過PC_1置換后，生成56位的密鑰"""return [bin_key[i - 1] for i in PC_1]  # 列表形式def shift_left(bin_key, num):"""實(shí)現(xiàn)C和D的循環(huán)左移"""return bin_key[num:] + bin_key[:num]def pc_2_change(bin_key):"""選擇壓縮56位的密鑰經(jīng)過PC_2壓縮，生成48位子密鑰"""return ''.join([bin_key[i - 1] for i in PC_2])  # 列表轉(zhuǎn)字符串def get_subkey_list(bin_key):"""生成16輪的加解子密鑰"""subkey_list = []  # 存儲(chǔ)16輪子密鑰# 1. 初始置換 64->58temp = pc_1_change(bin_key)# 2. 循環(huán)左移for i in shift_num:temp[:28] = shift_left(temp[:28], i)  # C部分循環(huán)左移temp[28:] = shift_left(temp[28:], i)  # D部分循環(huán)左移subkey_list.append(pc_2_change(temp))  # 生成子密鑰return subkey_list

2.2 DES加解密實(shí)現(xiàn)

# ========================================
# 二、DES加解密實(shí)現(xiàn)
# ========================================# 初始置換表IP 64->64
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]# 逆置換表_IP 64->64
_IP = [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]# 擴(kuò)展置換表E 32->48
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]# S盒 48->32
S1 = [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]
S2 = [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]
S3 = [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]
S4 = [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]
S5 = [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]
S6 = [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]
S7 = [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]
S8 = [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]
S = [S1, S2, S3, S4, S5, S6, S7, S8]# P盒
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]# encrypt
def ip_change(bin_text):"""初始置換"""return [bin_text[i - 1] for i in IP]def s_box(bin_result):"""S盒替換"""int_result = []result = ''for i in range(8):# 二進(jìn)制行號(hào)bin_row = bin_result[i][0] + bin_result[i][5]# 二進(jìn)制列號(hào)bin_col = ''.join(bin_result[i][j] for j in range(1, 5))# 獲取對(duì)應(yīng)的十進(jìn)制數(shù)int_result.append(S[i][16 * int(bin_row, base=2) + int(bin_col, base=2)])# 十進(jìn)制轉(zhuǎn)成二進(jìn)制result += bin(int_result[-1])[2:].zfill(4)return resultdef p_box(result):"""P盒置換"""return ''.join(result[i - 1] for i in P)def f(R, bin_key):"""輪函數(shù)f()"""# 1.將R由32位擴(kuò)展成48位R_ext = [R[i - 1] for i in E]# 2.與子密鑰進(jìn)行逐位異或bin_temp = [str(int(r) ^ int(k)) for r, k in zip(R_ext, bin_key)]# 6個(gè)字符為一組，共8組bin_result = [''.join(bin_temp[i:i + 6]) for i in range(0, len(bin_temp), 6)]# 3.S盒替換 48->32result = s_box(bin_result)# 4.P盒置換 32->32return p_box(result)def _ip_change(bin_text):"""進(jìn)行IP-1逆置換"""return ''.join(bin_text[i - 1] for i in _IP)def des_cipher(bin_text, bin_key, reverse_keys=False):"""通用DES加密解密函數(shù)"""# 1. 初始置換IPbin_text = ip_change(bin_text)# 2. 分成左右兩部分L、RL, R = bin_text[:32], bin_text[32:]# 3. 獲得16輪子密鑰subkey_list = get_subkey_list(bin_key)if reverse_keys:subkey_list = subkey_list[::-1]  # 解密時(shí)反轉(zhuǎn)子密鑰列表# 4. 進(jìn)行16輪迭代for i in subkey_list:R_temp = R# 輪函數(shù)f()結(jié)果和L進(jìn)行異或R = ''.join(str(int(r) ^ int(l)) for r, l in zip(f(R, i), L))L = R_temp# 5. 進(jìn)行IP-1逆置換 64->64return _ip_change(R + L)  # 輸出二進(jìn)制字符串# 使用示例
def str2bin(text):"""字符串轉(zhuǎn)二進(jìn)制字符串"""return ''.join(bin(byte)[2:].zfill(8) for byte in text.encode())def bin2str(bin_text):"""二進(jìn)制字符串轉(zhuǎn)字符串"""# 1.將二進(jìn)制字符串按8位分割，并轉(zhuǎn)換為字節(jié)數(shù)組byte_array = bytearray(int(i, 2) for i in re.findall(r'.{8}', bin_text) if int(i, 2) != 0)# 2.將字節(jié)序列解碼為字符串return byte_array.decode()def is_valid_key(key):"""檢查密鑰是否有效 64bit"""return len(key.encode()) == 8def des_encrypt(plaintext, key):"""DES加密"""# 1.明文轉(zhuǎn)成二進(jìn)制字符串, 0填充至64的倍數(shù)bin_plaintext = str2bin(plaintext)padding_len = (64 - (len(bin_plaintext) % 64)) % 64bin_padding_plaintext = bin_plaintext + '0' * padding_len# 2.進(jìn)行64位分組加密bin_group_64 = re.findall(r'.{64}', bin_padding_plaintext)bin_ciphertext = ''for g in bin_group_64:bin_ciphertext += des_cipher(g, str2bin(key))# 3.密文轉(zhuǎn)為16進(jìn)制輸出bin_group_4 = re.findall(r'.{4}', bin_ciphertext)hex_ciphertext = ''for g in bin_group_4:hex_ciphertext += format(int(g, 2), 'x')return hex_ciphertextdef des_decrypt(hex_ciphertext, key):"""DES解密"""# 1.16進(jìn)制密文轉(zhuǎn)為2進(jìn)制字符串bin_ciphertext = ''.join(bin(int(h, 16))[2:].zfill(4) for h in hex_ciphertext)# 2.進(jìn)行64位分組解密bin_group_64 = re.findall(r'.{64}', bin_ciphertext)bin_deciphertext = ''for g in bin_group_64:bin_deciphertext += des_cipher(g, str2bin(key), reverse_keys=True)# 3.將解密密文轉(zhuǎn)為字符串輸出return bin2str(bin_deciphertext)

2.3 完整代碼

import re# ========================================
# 一、子密鑰生成
# (1) 初始置換 64->56
# 64位的種子密鑰經(jīng)過PC_1置換后，生成56位的密鑰
# (2) 劃分 56->(28,28)
# 經(jīng)過初始置換后的56位密鑰被均分成C0和D0兩部分
# (3) 循環(huán)左移
# 第一輪，C0和D0根據(jù)移位次數(shù)表各自進(jìn)行循環(huán)左移
# 得到C1和D1
# 每一輪的C和D值是由上一輪的C和D值循環(huán)左移得到的
# (4) 合并 (28,28)->56->48
# 左移后的兩部分再次合并,通過一個(gè)選擇壓縮表(PC_2)
# 得到這一輪的子密鑰
# (5)重復(fù)3、4操作,最終得到16個(gè)子密鑰
# ========================================# 置換選擇表1(PC_1) 64->56
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]# 選擇壓縮表2(PC_2) 56->48
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]# 移位次數(shù)表
shift_num = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1]def pc_1_change(bin_key):"""初始置換64位的種子密鑰經(jīng)過PC_1置換后，生成56位的密鑰"""return [bin_key[i - 1] for i in PC_1]  # 列表形式def shift_left(bin_key, num):"""實(shí)現(xiàn)C和D的循環(huán)左移"""return bin_key[num:] + bin_key[:num]def pc_2_change(bin_key):"""選擇壓縮56位的密鑰經(jīng)過PC_2壓縮，生成48位子密鑰"""return ''.join([bin_key[i - 1] for i in PC_2])  # 列表轉(zhuǎn)字符串def get_subkey_list(bin_key):"""生成16輪的加解子密鑰"""subkey_list = []  # 存儲(chǔ)16輪子密鑰# 1. 初始置換 64->58temp = pc_1_change(bin_key)# 2. 循環(huán)左移for i in shift_num:temp[:28] = shift_left(temp[:28], i)  # C部分循環(huán)左移temp[28:] = shift_left(temp[28:], i)  # D部分循環(huán)左移subkey_list.append(pc_2_change(temp))  # 生成子密鑰return subkey_list# ========================================
# 二、DES加解密實(shí)現(xiàn)
# ========================================# 初始置換表IP 64->64
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]# 逆置換表_IP 64->64
_IP = [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]# 擴(kuò)展置換表E 32->48
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]# S盒 48->32
S1 = [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]
S2 = [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]
S3 = [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]
S4 = [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]
S5 = [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]
S6 = [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]
S7 = [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]
S8 = [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]
S = [S1, S2, S3, S4, S5, S6, S7, S8]# P盒
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]# encrypt
def ip_change(bin_text):"""初始置換"""return [bin_text[i - 1] for i in IP]def s_box(bin_result):"""S盒替換"""int_result = []result = ''for i in range(8):# 二進(jìn)制行號(hào)bin_row = bin_result[i][0] + bin_result[i][5]# 二進(jìn)制列號(hào)bin_col = ''.join(bin_result[i][j] for j in range(1, 5))# 獲取對(duì)應(yīng)的十進(jìn)制數(shù)int_result.append(S[i][16 * int(bin_row, base=2) + int(bin_col, base=2)])# 十進(jìn)制轉(zhuǎn)成二進(jìn)制result += bin(int_result[-1])[2:].zfill(4)return resultdef p_box(result):"""P盒置換"""return ''.join(result[i - 1] for i in P)def f(R, bin_key):"""輪函數(shù)f()"""# 1.將R由32位擴(kuò)展成48位R_ext = [R[i - 1] for i in E]# 2.與子密鑰進(jìn)行逐位異或bin_temp = [str(int(r) ^ int(k)) for r, k in zip(R_ext, bin_key)]# 6個(gè)字符為一組，共8組bin_result = [''.join(bin_temp[i:i + 6]) for i in range(0, len(bin_temp), 6)]# 3.S盒替換 48->32result = s_box(bin_result)# 4.P盒置換 32->32return p_box(result)def _ip_change(bin_text):"""進(jìn)行IP-1逆置換"""return ''.join(bin_text[i - 1] for i in _IP)def des_cipher(bin_text, bin_key, reverse_keys=False):"""通用DES加密解密函數(shù)"""# 1. 初始置換IPbin_text = ip_change(bin_text)# 2. 分成左右兩部分L、RL, R = bin_text[:32], bin_text[32:]# 3. 獲得16輪子密鑰subkey_list = get_subkey_list(bin_key)if reverse_keys:subkey_list = subkey_list[::-1]  # 解密時(shí)反轉(zhuǎn)子密鑰列表# 4. 進(jìn)行16輪迭代for i in subkey_list:R_temp = R# 輪函數(shù)f()結(jié)果和L進(jìn)行異或R = ''.join(str(int(r) ^ int(l)) for r, l in zip(f(R, i), L))L = R_temp# 5. 進(jìn)行IP-1逆置換 64->64return _ip_change(R + L)  # 輸出二進(jìn)制字符串# 使用示例
def str2bin(text):"""字符串轉(zhuǎn)二進(jìn)制字符串"""return ''.join(bin(byte)[2:].zfill(8) for byte in text.encode())def bin2str(bin_text):"""二進(jìn)制字符串轉(zhuǎn)字符串"""# 1.將二進(jìn)制字符串按8位分割，并轉(zhuǎn)換為字節(jié)數(shù)組byte_array = bytearray(int(i, 2) for i in re.findall(r'.{8}', bin_text) if int(i, 2) != 0)# 2.將字節(jié)序列解碼為字符串return byte_array.decode()def is_valid_key(key):"""檢查密鑰是否有效 64bit"""return len(key.encode()) == 8def des_encrypt(plaintext, key):"""DES加密"""# 1.明文轉(zhuǎn)成二進(jìn)制字符串, 0填充至64的倍數(shù)bin_plaintext = str2bin(plaintext)padding_len = (64 - (len(bin_plaintext) % 64)) % 64bin_padding_plaintext = bin_plaintext + '0' * padding_len# 2.進(jìn)行64位分組加密bin_group_64 = re.findall(r'.{64}', bin_padding_plaintext)bin_ciphertext = ''for g in bin_group_64:bin_ciphertext += des_cipher(g, str2bin(key))# 3.密文轉(zhuǎn)為16進(jìn)制輸出bin_group_4 = re.findall(r'.{4}', bin_ciphertext)hex_ciphertext = ''for g in bin_group_4:hex_ciphertext += format(int(g, 2), 'x')return hex_ciphertextdef des_decrypt(hex_ciphertext, key):"""DES解密"""# 1.16進(jìn)制密文轉(zhuǎn)為2進(jìn)制字符串bin_ciphertext = ''.join(bin(int(h, 16))[2:].zfill(4) for h in hex_ciphertext)# 2.進(jìn)行64位分組解密bin_group_64 = re.findall(r'.{64}', bin_ciphertext)bin_deciphertext = ''for g in bin_group_64:bin_deciphertext += des_cipher(g, str2bin(key), reverse_keys=True)# 3.將解密密文轉(zhuǎn)為字符串輸出return bin2str(bin_deciphertext)def des_run():"""DES啟動(dòng)界面"""flag = Truewhile flag:print('=' * 3, "DES加密解密", '=' * 3)print('[1]加密')print('[2]解密')print('[0]退出')choice = input('請(qǐng)輸入你的選擇：')match choice:case '0':flag = Falsecase '1':plaintext = input('請(qǐng)輸入明文:')key = input('請(qǐng)輸入密鑰(64bit):')if not is_valid_key(key):print('密鑰長(zhǎng)度錯(cuò)誤')continueciphertext = des_encrypt(plaintext, key)print(f'密文:{ciphertext}')case '2':ciphertext = input('請(qǐng)輸入密文:')key = input('請(qǐng)輸入密鑰(64bit):')if not is_valid_key(key):print('密鑰長(zhǎng)度錯(cuò)誤')continueprint(f'解密:{des_decrypt(ciphertext, key)}')case _:print('輸入錯(cuò)誤')print('=' * 15)if __name__ == '__main__':des_run()

三、演示效果