AES加解密（默认ECB模式）代码原理实现

aes.py:

# 加密时用的S盒
SBox = (
    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,
)

# 解密时用的S盒
InvSBox = (
    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,
)

# 轮常数，用于轮密钥的产生
RCON = (
    0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40,
    0x80, 0x1B, 0x36, 0x6C, 0xD8, 0xAB, 0x4D, 0x9A,
    0x2F, 0x5E, 0xBC, 0x63, 0xC6, 0x97, 0x35, 0x6A,
    0xD4, 0xB3, 0x7D, 0xFA, 0xEF, 0xC5, 0x91, 0x39,
)

# GF(2⁸)上的乘2运算——xtime的计算公式
xtime = lambda a: (((a << 1) ^ 0x1B) & 0xFF) if (a & 0x80) else (a << 1)


class AES:
    def __init__(self, master_key):
        """初始化AES加密器"""
        self.round_keys = self._key_expansion(master_key)

    def _key_expansion(self, master_key):
        """密钥扩展"""
        round_keys = self.text2matrix(master_key)

        for i in range(4, 44):  # AES-128-128需要44个字(11轮)
            temp = round_keys[i - 1]
            if i % 4 == 0:
                # 字循环、字节代换和轮常数异或
                temp = [SBox[temp[1]] ^ RCON[i // 4],
                        SBox[temp[2]],
                        SBox[temp[3]],
                        SBox[temp[0]]]

            # 生成新轮密钥字
            new_word = [round_keys[i - 4][j] ^ temp[j] for j in range(4)]
            round_keys.append(new_word)

        return round_keys

    def encrypt(self, plaintext):
        """加密128位数据块"""
        state = self.text2matrix(plaintext)

        self._add_round_key(state, self.round_keys[:4])

        for round_num in range(1, 10):
            self._sub_bytes(state)
            self._shift_rows(state)
            self._mix_columns(state)
            self._add_round_key(state, self.round_keys[4 * round_num:4 * (round_num + 1)])

        self._sub_bytes(state)
        self._shift_rows(state)
        self._add_round_key(state, self.round_keys[40:])

        return self.matrix2text(state)

    def decrypt(self, ciphertext):
        """解密128位数据块"""
        state = self.text2matrix(ciphertext)

        self._add_round_key(state, self.round_keys[40:])
        self._inv_shift_rows(state)
        self._inv_sub_bytes(state)

        for round_num in range(9, 0, -1):
            self._add_round_key(state, self.round_keys[4 * round_num:4 * (round_num + 1)])
            self._inv_mix_columns(state)
            self._inv_shift_rows(state)
            self._inv_sub_bytes(state)

        self._add_round_key(state, self.round_keys[:4])

        return self.matrix2text(state)

    @staticmethod
    def text2matrix(text):
        """将128位整数text转换为4*4矩阵(列优先)"""
        matrix = [[] for _ in range(4)]  # 初始化4列
        for i in range(16):
            byte = (text >> (8 * (15 - i))) & 0xFF
            matrix[i // 4].append(byte)  # 按列填充
        return matrix

    @staticmethod
    def matrix2text(matrix):
        """将4*4矩阵转换为128位整数text(列优先)"""
        text = 0
        for i in range(4):
            for j in range(4):
                text |= (matrix[i][j] << (120 - 8 * (4 * i + j)))
        return text

    @staticmethod
    def _add_round_key(s, k):
        """轮密钥加"""
        for i in range(4):
            for j in range(4):
                s[i][j] ^= k[i][j]

    @staticmethod
    def _sub_bytes(s):
        """字节代换"""
        for i in range(4):
            for j in range(4):
                s[i][j] = SBox[s[i][j]]

    @staticmethod
    def _inv_sub_bytes(s):
        """逆字节代换"""
        for i in range(4):
            for j in range(4):
                s[i][j] = InvSBox[s[i][j]]

    @staticmethod
    def _shift_rows(s):
        """行移位"""
        s[0][1], s[1][1], s[2][1], s[3][1] = s[1][1], s[2][1], s[3][1], s[0][1]
        s[0][2], s[1][2], s[2][2], s[3][2] = s[2][2], s[3][2], s[0][2], s[1][2]
        s[0][3], s[1][3], s[2][3], s[3][3] = s[3][3], s[0][3], s[1][3], s[2][3]

    @staticmethod
    def _inv_shift_rows(s):
        """逆行移位"""
        s[0][1], s[1][1], s[2][1], s[3][1] = s[3][1], s[0][1], s[1][1], s[2][1]
        s[0][2], s[1][2], s[2][2], s[3][2] = s[2][2], s[3][2], s[0][2], s[1][2]
        s[0][3], s[1][3], s[2][3], s[3][3] = s[1][3], s[2][3], s[3][3], s[0][3]

    @staticmethod
    def _mix_columns(s):
        """列混合"""
        for i in range(4):
            t = s[i][0] ^ s[i][1] ^ s[i][2] ^ s[i][3]
            u = s[i][0]
            s[i][0] ^= t ^ xtime(s[i][0] ^ s[i][1])
            s[i][1] ^= t ^ xtime(s[i][1] ^ s[i][2])
            s[i][2] ^= t ^ xtime(s[i][2] ^ s[i][3])
            s[i][3] ^= t ^ xtime(s[i][3] ^ u)

    @staticmethod
    def _inv_mix_columns(s):
        """逆列混合"""
        for i in range(4):
            u = xtime(xtime(s[i][0] ^ s[i][2]))
            v = xtime(xtime(s[i][1] ^ s[i][3]))
            s[i][0] ^= u
            s[i][1] ^= v
            s[i][2] ^= u
            s[i][3] ^= v

        AES._mix_columns(s)

test.py:

from aes import AES


def format_hex(value):
    return f"0x{value:032x}"


def encrypt_data(aes, plaintext):
    """加密函数"""
    print(f"Plaintext: {format_hex(plaintext)}")
    encrypted = aes.encrypt(plaintext)
    print(f"Encrypted: {format_hex(encrypted)}\n")


def decrypt_data(aes, ciphertext):
    """解密函数"""
    print(f"Ciphertext: {format_hex(ciphertext)}")
    decrypted = aes.decrypt(ciphertext)
    print(f"Decrypted: {format_hex(decrypted)}\n")


def test():
    # 外部定义的密钥
    master_key = 0x2b7e151628aed2a6abf7158809cf4f3c
    aes = AES(master_key)

    plaintext = 0x00112233445566778899aabbccddeeff
    ciphertext = 0x7df76b0c1ab899b33e42f047b91b546f

    encrypt_data(aes, plaintext)
    decrypt_data(aes, ciphertext)


if __name__ == "__main__":
    test()