不使用python标准库实现DES加解密

好的，以下是一个不使用Python标准库实现DES加解密的示例：

# S-Box表
S_BOX = [
    [1, 0, 3, 2],
    [3, 2, 1, 0],
    [0, 2, 1, 3],
    [3, 1, 3, 2]
]

# 初始置换表
INITIAL_PERMUTATION = [
    1, 5, 2, 0, 3, 7, 4, 6
]

# 逆置换表
INVERSE_PERMUTATION = [
    3, 0, 2, 4, 6, 1, 7, 5
]

# 扩展置换表
EXPANSION_PERMUTATION = [
    3, 0, 1, 2, 1, 2, 3, 0
]

# P-Box置换表
P_BOX_PERMUTATION = [
    1, 3, 2, 0
]

# 子密钥生成表
SUB_KEY_GENERATION_TABLE = [
    0, 1, 2, 3, 2, 3, 4, 5, 4, 5, 6, 7, 6, 7, 8, 9,
    8, 9, 10, 11, 10, 11, 12, 13, 12, 13, 14, 15, 14, 15, 0, 1
]

# 将字节数组转换为64位二进制字符串
def byte_array_to_binary_string(byte_array):
    return ''.join(format(byte, '08b') for byte in byte_array)

# 将64位二进制字符串转换为字节数组
def binary_string_to_byte_array(binary_string):
    return [int(binary_string[i:i+8], 2) for i in range(0, len(binary_string), 8)]

# 对64位数据块进行初始置换
def initial_permutation(block):
    return [block[INITIAL_PERMUTATION[i]] for i in range(8)]

# 对64位数据块进行逆置换
def inverse_permutation(block):
    return [block[INVERSE_PERMUTATION[i]] for i in range(8)]

# 将8位二进制字符串转换为4位十六进制字符串
def binary_string_to_hex_string(binary_string):
    return hex(int(binary_string, 2))[2:].zfill(2)

# 将4位十六进制字符串转换为8位二进制字符串
def hex_string_to_binary_string(hex_string):
    return bin(int(hex_string, 16))[2:].zfill(8)

# 对32位数据块进行S-Box置换
def s_box_substitution(block):
    result = ''
    for i in range(0, len(block), 4):
        row = int(block[i] + block[i+3], 2)
        col = int(block[i+1] + block[i+2], 2)
        result += '{0:02b}'.format(S_BOX[row][col])
    return result

# 对32位数据块进行扩展置换
def expansion_permutation(block):
    return [block[EXPANSION_PERMUTATION[i]] for i in range(8)]

# 对48位数据块和48位子密钥进行异或运算
def xor(block, sub_key):
    return ''.join(str(int(block[i]) ^ int(sub_key[i])) for i in range(48))

# 对32位数据块进行P-Box置换
def p_box_permutation(block):
    return [block[P_BOX_PERMUTATION[i]] for i in range(4)]

# 生成16个子密钥
def generate_sub_keys(key):
    binary_key = byte_array_to_binary_string(key)
    permuted_key = [binary_key[i] for i in range(56)]
    sub_keys = []
    for i in range(16):
        # 循环左移
        left_half = permuted_key[:28]
        right_half = permuted_key[28:]
        left_half = left_half[SUB_KEY_GENERATION_TABLE[i]:] + left_half[:SUB_KEY_GENERATION_TABLE[i]]
        right_half = right_half[SUB_KEY_GENERATION_TABLE[i]:] + right_half[:SUB_KEY_GENERATION_TABLE[i]]
        permuted_key = left_half + right_half
        # 选择置换
        selected_key = [permuted_key[i] for i in range(48) if (i+1) % 6 != 0]
        sub_keys.append(selected_key)
    return sub_keys

# DES加密函数
def des_encrypt(key, data):
    sub_keys = generate_sub_keys(key)
    binary_data = byte_array_to_binary_string(data)
    blocks = [binary_data[i:i+64] for i in range(0, len(binary_data), 64)]
    result = ''
    for block in blocks:
        # 初始置换
        block = initial_permutation(block)
        left_half = block[:4]
        right_half = block[4:]
        for i in range(16):
            # 扩展置换
            expanded_right_half = expansion_permutation(right_half)
            # 异或运算
            xored_block = xor(expanded_right_half, sub_keys[i])
            # S-Box置换
            s_box_substituted_block = s_box_substitution(xored_block)
            # P-Box置换
            p_box_permuted_block = p_box_permutation(s_box_substituted_block)
            # 左右交换
            new_right_half = [str(int(left_half[j]) ^ int(p_box_permuted_block[j])) for j in range(4)]
            left_half = right_half
            right_half = new_right_half
        # 逆置换
        block = inverse_permutation(right_half + left_half)
        result += ''.join(binary_string_to_hex_string(''.join(block[i:i+4])) for i in range(0, len(block), 4))
    return bytes.fromhex(result)

# DES解密函数
def des_decrypt(key, data):
    sub_keys = generate_sub_keys(key)
    binary_data = byte_array_to_binary_string(data)
    blocks = [binary_data[i:i+64] for i in range(0, len(binary_data), 64)]
    result = ''
    for block in blocks:
        # 初始置换
        block = initial_permutation(block)
        left_half = block[:4]
        right_half = block[4:]
        for i in range(15, -1, -1):
            # 扩展置换
            expanded_right_half = expansion_permutation(right_half)
            # 异或运算
            xored_block = xor(expanded_right_half, sub_keys[i])
            # S-Box置换
            s_box_substituted_block = s_box_substitution(xored_block)
            # P-Box置换
            p_box_permuted_block = p_box_permutation(s_box_substituted_block)
            # 左右交换
            new_right_half = [str(int(left_half[j]) ^ int(p_box_permuted_block[j])) for j in range(4)]
            left_half = right_half
            right_half = new_right_half
        # 逆置换
        block = inverse_permutation(right_half + left_half)
        result += ''.join(binary_string_to_hex_string(''.join(block[i:i+4])) for i in range(0, len(block), 4))
    return bytes.fromhex(result)

注意，这个实现中的DES算法也已经被证明不是安全的加密算法，不应在实际应用中使用。