aes.py

from utils import b2matrix, matrix2b, xor_bytes

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,
)



def shift_rows(s, operations_per_round=None):
    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]
    if operations_per_round:
        operations_per_round['perm']+=12*8
        # print('shift_rows 12')
    return operations_per_round


def inv_shift_rows(s):
    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]

def add_round_key(s, k, operations_per_round=None):
    for i in range(4):
        for j in range(4):
            s[i][j] ^= k[i][j]
            # if operations_per_round:
            #     operations_per_round['xor']+=1*8
    if operations_per_round:
        operations_per_round['xor']=i*j*8
        # print(f'XOR {i*j}')
    return operations_per_round


# learned from https://web.archive.org/web/20100626212235/http://cs.ucsb.edu/~koc/cs178/projects/JT/aes.c
xtime = lambda a: (((a << 1) ^ 0x1B) & 0xFF) if (a & 0x80) else (a << 1)


def mix_single_column(a, operations_per_round=None):
    # see Sec 4.1.2 in The Design of Rijndael
    t = a[0] ^ a[1] ^ a[2] ^ a[3]
    u = a[0]
    a[0] ^= t ^ xtime(a[0] ^ a[1])
    a[1] ^= t ^ xtime(a[1] ^ a[2])
    a[2] ^= t ^ xtime(a[2] ^ a[3])
    a[3] ^= t ^ xtime(a[3] ^ u)

    # if operations_per_round:
    #     operations_per_round['perm']+=4*8
    return operations_per_round


def mix_columns(s, operations_per_round=None):
    for i in range(4):
        operations_per_round = mix_single_column(s[i], operations_per_round)

    if operations_per_round:
        operations_per_round['perm']+=i*4*8
    return operations_per_round


def inv_mix_columns(s):
    # see Sec 4.1.3 in The Design of Rijndael
    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

    mix_columns(s)


r_con = (
    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,
)

def sub_bytes(s, operations_per_round=None):
    for i in range(4):
        for j in range(4):
            s[i][j] = s_box[s[i][j]]
            # if operations_per_round:
            #     operations_per_round['sub']+=8
    if operations_per_round:
        operations_per_round['sub']=i*j*8
    #     print(f'Sub {i*j}')
    return operations_per_round


def inv_sub_bytes(s):
    for i in range(4):
        for j in range(4):
            s[i][j] = inv_s_box[s[i][j]]


class AES:
    """
    Class for AES-128 encryption
    """
    rounds_by_key_size = {16: 10, 24: 12, 32: 14}
    def __init__(self, master_key):
        """
        Initializes the object with a given key.
        """
        assert len(master_key) in AES.rounds_by_key_size
        self.n_rounds = AES.rounds_by_key_size[len(master_key)]
        self._key_matrices = self._expand_key(master_key)

        self.operations_all_rounds = {'sub':0, 'perm':0, 'xor':0}

    def _expand_key(self, master_key):
        """
        Expands and returns a list of key matrices for the given master_key.
        """
        # Initialize round keys with raw key material.
        key_columns = b2matrix(master_key)
        iteration_size = len(master_key) // 4

        i = 1
        while len(key_columns) < (self.n_rounds + 1) * 4:
            # Copy previous word.
            word = list(key_columns[-1])

            # Perform schedule_core once every "row".
            if len(key_columns) % iteration_size == 0:
                # Circular shift.
                word.append(word.pop(0))
                # Map to S-BOX.
                word = [s_box[b] for b in word]
                # XOR with first byte of R-CON, since the others bytes of R-CON are 0.
                word[0] ^= r_con[i]
                i += 1
            elif len(master_key) == 32 and len(key_columns) % iteration_size == 4:
                # Run word through S-box in the fourth iteration when using a
                # 256-bit key.
                word = [s_box[b] for b in word]

            # XOR with equivalent word from previous iteration.
            word = xor_bytes(word, key_columns[-iteration_size])
            key_columns.append(word)

        # Group key words in 4x4 byte matrices.
        return [key_columns[4*i : 4*(i+1)] for i in range(len(key_columns) // 4)]

    def encrypt_block(self, plaintext):
        """
        Encrypts a single block of 16 byte long plaintext.
        """
        assert len(plaintext) == 16

        plain_state = b2matrix(plaintext)

        _ =add_round_key(plain_state, self._key_matrices[0])

        for i in range(1, self.n_rounds):
            if i==1:
                operations_per_round = {'sub':0, 'perm':0, 'xor':0}
            else:
                operations_per_round = None

            operations_per_round=sub_bytes(plain_state, operations_per_round)
            operations_per_round=shift_rows(plain_state, operations_per_round)
            operations_per_round=mix_columns(plain_state, operations_per_round)
            operations_per_round=add_round_key(plain_state, self._key_matrices[i], operations_per_round)

            if i ==1:
                self.operations_one_round = operations_per_round

        for k in self.operations_one_round.keys():
            self.operations_all_rounds[k]+=self.operations_one_round[k]*self.n_rounds

        _ = sub_bytes(plain_state)
        _ = shift_rows(plain_state)
        _ = add_round_key(plain_state, self._key_matrices[-1])

        return matrix2b(plain_state)

    def decrypt_block(self, ciphertext):
        """
        Decrypts a single block of 16 byte long ciphertext.
        """
        assert len(ciphertext) == 16

        cipher_state = b2matrix(ciphertext)

        _ = add_round_key(cipher_state, self._key_matrices[-1])
        inv_shift_rows(cipher_state)
        inv_sub_bytes(cipher_state)

        for i in range(self.n_rounds - 1, 0, -1):
            _ = add_round_key(cipher_state, self._key_matrices[i])
            inv_mix_columns(cipher_state)
            inv_shift_rows(cipher_state)
            inv_sub_bytes(cipher_state)

        _ = add_round_key(cipher_state, self._key_matrices[0])

        return matrix2b(cipher_state)