信息安全密码学基础 - 实验代码

import os

# AES块大小
BLOCK_SIZE = 16


# 生成随机字节
def generate_random_bytes(length):
    return os.urandom(length)


# 填充函数：PKCS#7
def pad(data):
    pad_length = BLOCK_SIZE - len(data) % BLOCK_SIZE
    return data + bytes([pad_length] * pad_length)


# 去填充函数：PKCS#7
def unpad(data):
    pad_length = data[-1]
    return data[:-pad_length]


# 定义S盒和逆S盒
s_box = [
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
]

inv_s_box = [
    0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
    0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
    0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
    0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
    0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
    0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
    0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
    0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
    0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
    0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
    0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
    0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
    0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
    0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
    0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
]


# 字节替换
def sub_bytes(state):
    return bytes(s_box[b] for b in state)


# 字节替换的逆操作
def inv_sub_bytes(state):
    return bytes(inv_s_box[b] for b in state)


# 行移位
def shift_rows(state):
    return bytes([
        state[0], state[5], state[10], state[15],
        state[4], state[9], state[14], state[3],
        state[8], state[13], state[2], state[7],
        state[12], state[1], state[6], state[11],
    ])


# 行移位的逆操作
def inv_shift_rows(state):
    return bytes([
        state[0], state[13], state[10], state[7],
        state[4], state[1], state[14], state[11],
        state[8], state[5], state[2], state[15],
        state[12], state[9], state[6], state[3],
    ])


# GF(2^8)中的乘法
def gmul(a, b):
    p = 0
    for _ in range(8):
        if b & 1:
            p ^= a
        hi_bit_set = a & 0x80
        a <<= 1
        if hi_bit_set:
            a ^= 0x1b
        b >>= 1
    return p & 0xff


# 列混合
def mix_columns(state):
    mixed = bytearray(16)
    for i in range(4):
        mixed[i * 4 + 0] = gmul(state[i * 4 + 0], 2) ^ gmul(state[i * 4 + 1], 3) ^ state[i * 4 + 2] ^ state[i * 4 + 3]
        mixed[i * 4 + 1] = state[i * 4 + 0] ^ gmul(state[i * 4 + 1], 2) ^ gmul(state[i * 4 + 2], 3) ^ state[i * 4 + 3]
        mixed[i * 4 + 2] = state[i * 4 + 0] ^ state[i * 4 + 1] ^ gmul(state[i * 4 + 2], 2) ^ gmul(state[i * 4 + 3], 3)
        mixed[i * 4 + 3] = gmul(state[i * 4 + 0], 3) ^ state[i * 4 + 1] ^ state[i * 4 + 2] ^ gmul(state[i * 4 + 3], 2)
    return bytes(mixed)


# 列混合的逆操作
def inv_mix_columns(state):
    mixed = bytearray(16)
    for i in range(4):
        mixed[i * 4 + 0] = gmul(state[i * 4 + 0], 14) ^ gmul(state[i * 4 + 1], 11) ^ gmul(state[i * 4 + 2], 13) ^ gmul(
            state[i * 4 + 3], 9)
        mixed[i * 4 + 1] = gmul(state[i * 4 + 0], 9) ^ gmul(state[i * 4 + 1], 14) ^ gmul(state[i * 4 + 2], 11) ^ gmul(
            state[i * 4 + 3], 13)
        mixed[i * 4 + 2] = gmul(state[i * 4 + 0], 13) ^ gmul(state[i * 4 + 1], 9) ^ gmul(state[i * 4 + 2], 14) ^ gmul(
            state[i * 4 + 3], 11)
        mixed[i * 4 + 3] = gmul(state[i * 4 + 0], 11) ^ gmul(state[i * 4 + 1], 13) ^ gmul(state[i * 4 + 2], 9) ^ gmul(
            state[i * 4 + 3], 14)
    return bytes(mixed)


# 轮密钥加
def add_round_key(state, round_key):
    return bytes(a ^ b for a, b in zip(state, round_key))


# AES块加密函数
def aes_encrypt_block(block, key):
    state = add_round_key(block, key)
    for _ in range(9):
        state = sub_bytes(state)
        state = shift_rows(state)
        state = mix_columns(state)
        state = add_round_key(state, key)
    state = sub_bytes(state)
    state = shift_rows(state)
    state = add_round_key(state, key)
    return state


# AES块解密函数
def aes_decrypt_block(block, key):
    state = add_round_key(block, key)
    state = inv_shift_rows(state)
    state = inv_sub_bytes(state)
    for _ in range(9):
        state = add_round_key(state, key)
        state = inv_mix_columns(state)
        state = inv_shift_rows(state)
        state = inv_sub_bytes(state)
    state = add_round_key(state, key)
    return state


# CBC模式加密
def aes_cbc_encrypt(key, plaintext):
    iv = generate_random_bytes(BLOCK_SIZE)  # 生成随机初始化向量（IV）
    plaintext_padded = pad(plaintext.encode('utf-8'))
    ciphertext = iv
    previous_block = iv

    for i in range(0, len(plaintext_padded), BLOCK_SIZE):
        plaintext_block = plaintext_padded[i:i + BLOCK_SIZE]
        xor_block = bytes(a ^ b for a, b in zip(plaintext_block, previous_block))
        encrypted_block = aes_encrypt_block(xor_block, key)
        ciphertext += encrypted_block
        previous_block = encrypted_block

    return ciphertext


# CBC模式解密
def aes_cbc_decrypt(key, ciphertext):
    iv = ciphertext[:BLOCK_SIZE]
    actual_ciphertext = ciphertext[BLOCK_SIZE:]
    previous_block = iv
    plaintext_padded = b''

    for i in range(0, len(actual_ciphertext), BLOCK_SIZE):
        ciphertext_block = actual_ciphertext[i:i + BLOCK_SIZE]
        decrypted_block = aes_decrypt_block(ciphertext_block, key)
        plaintext_block = bytes(a ^ b for a, b in zip(decrypted_block, previous_block))
        plaintext_padded += plaintext_block
        previous_block = ciphertext_block

    plaintext = unpad(plaintext_padded)
    return plaintext.decode('utf-8')


# OFB模式加密
def aes_ofb_encrypt(key, plaintext):
    iv = generate_random_bytes(BLOCK_SIZE)  # 生成随机初始化向量（IV）
    plaintext_bytes = plaintext.encode('utf-8')
    ciphertext = iv
    previous_block = iv

    for i in range(0, len(plaintext_bytes), BLOCK_SIZE):
        block = plaintext_bytes[i:i + BLOCK_SIZE]
        encrypted_block = aes_encrypt_block(previous_block, key)
        cipher_block = bytes(a ^ b for a, b in zip(block, encrypted_block))
        ciphertext += cipher_block
        previous_block = encrypted_block

    return ciphertext


# OFB模式解密
def aes_ofb_decrypt(key, ciphertext):
    iv = ciphertext[:BLOCK_SIZE]
    actual_ciphertext = ciphertext[BLOCK_SIZE:]
    previous_block = iv
    plaintext_bytes = b''

    for i in range(0, len(actual_ciphertext), BLOCK_SIZE):
        ciphertext_block = actual_ciphertext[i:i + BLOCK_SIZE]
        encrypted_block = aes_encrypt_block(previous_block, key)
        plaintext_block = bytes(a ^ b for a, b in zip(ciphertext_block, encrypted_block))
        plaintext_bytes += plaintext_block
        previous_block = encrypted_block

    return plaintext_bytes.decode('utf-8')


# 生成AES密钥
def generate_aes_key():
    return generate_random_bytes(BLOCK_SIZE)


def main():
    message = "26221013_Daaihang_Wong"  # 学号+姓名
    print(f"原始消息: {message}")

    # 生成AES密钥
    aes_key = generate_aes_key()

    # CBC模式
    encrypted_message_cbc = aes_cbc_encrypt(aes_key, message)
    print(f"CBC模式加密后的消息: {encrypted_message_cbc}")
    decrypted_message_cbc = aes_cbc_decrypt(aes_key, encrypted_message_cbc)
    print(f"CBC模式解密后的消息: {decrypted_message_cbc}")

    # OFB模式
    encrypted_message_ofb = aes_ofb_encrypt(aes_key, message)
    print(f"OFB模式加密后的消息: {encrypted_message_ofb}")
    decrypted_message_ofb = aes_ofb_decrypt(aes_key, encrypted_message_ofb)
    print(f"OFB模式解密后的消息: {decrypted_message_ofb}")

    # 检查解密后的消息是否正确
    assert message == decrypted_message_cbc, "CBC模式解密失败！"
    assert message == decrypted_message_ofb, "OFB模式解密失败！"
    print("CBC和OFB模式解密成功！")


if __name__ == "__main__":
    main()