A simple/simplistic implementation of AES in pure Python.

aes.py

#My AES implementation
# By Daniel Miller

def xor(s1, s2):
    return tuple(a^b for a,b in zip(s1, s2))

class AES(object):
    class __metaclass__(type):
        def __init__(cls, name, bases, classdict):
            cls.Gmul = {}
            for f in (0x02, 0x03, 0x0e, 0x0b, 0x0d, 0x09):
                cls.Gmul[f] = tuple(cls.gmul(f, x) for x in range(0,0x100))

    Rcon = ( 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a )
    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
            )
    Sbox_inv = (
            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
            )

    @staticmethod
    def rot_word(word):
        return word[1:] + word[:1]

    @staticmethod
    def sub_word(word):
        return (AES.Sbox[b] for b in word)

    def key_schedule(self):
        expanded = []
        expanded.extend(map(ord, self.key))
        for i in range(self.nk, self.nb * (self.nr + 1)):
            t = expanded[(i-1)*4:i*4]
            if i % self.nk == 0:
                t = xor( AES.sub_word( AES.rot_word(t) ), (AES.Rcon[i // self.nk],0,0,0) )
            elif self.nk > 6 and i % self.nk == 4:
                t = AES.sub_word(t)
            expanded.extend( xor(t, expanded[(i-self.nk)*4:(i-self.nk+1)*4]))
        return expanded

    def add_round_key(self, rkey):
        for i, b in enumerate(rkey):
            self.state[i] ^= b

    def sub_bytes(self):
        for i, b in enumerate(self.state):
            self.state[i] = AES.Sbox[b]

    def inv_sub_bytes(self):
        for i, b in enumerate(self.state):
            self.state[i] = AES.Sbox_inv[b]

    def shift_rows(self):
        rows = []
        for r in range(4):
            rows.append( self.state[r::4] )
            rows[r] = rows[r][r:] + rows[r][:r]
        self.state = [ r[c] for c in range(4) for r in rows ]

    def inv_shift_rows(self):
        rows = []
        for r in range(4):
            rows.append( self.state[r::4] )
            rows[r] = rows[r][4-r:] + rows[r][:4-r]
        self.state = [ r[c] for c in range(4) for r in rows ]

    @staticmethod
    def gmul(a, b):
        p = 0
        for c in range(8):
            if b & 1:
                p ^= a
            a <<= 1
            if a & 0x100:
                a ^= 0x11b
            b >>= 1
        return p

    def mix_columns(self):
        ss = []
        for c in range(4):
            col = self.state[c*4:(c+1)*4]
            ss.extend((
                        AES.Gmul[0x02][col[0]] ^ AES.Gmul[0x03][col[1]] ^                col[2]  ^                col[3] ,
                                       col[0]  ^ AES.Gmul[0x02][col[1]] ^ AES.Gmul[0x03][col[2]] ^                col[3] ,
                                       col[0]  ^                col[1]  ^ AES.Gmul[0x02][col[2]] ^ AES.Gmul[0x03][col[3]],
                        AES.Gmul[0x03][col[0]] ^                col[1]  ^                col[2]  ^ AES.Gmul[0x02][col[3]],
                    ))
        self.state = ss

    def inv_mix_columns(self):
        ss = []
        for c in range(4):
            col = self.state[c*4:(c+1)*4]
            ss.extend((
                        AES.Gmul[0x0e][col[0]] ^ AES.Gmul[0x0b][col[1]] ^ AES.Gmul[0x0d][col[2]] ^ AES.Gmul[0x09][col[3]],
                        AES.Gmul[0x09][col[0]] ^ AES.Gmul[0x0e][col[1]] ^ AES.Gmul[0x0b][col[2]] ^ AES.Gmul[0x0d][col[3]],
                        AES.Gmul[0x0d][col[0]] ^ AES.Gmul[0x09][col[1]] ^ AES.Gmul[0x0e][col[2]] ^ AES.Gmul[0x0b][col[3]],
                        AES.Gmul[0x0b][col[0]] ^ AES.Gmul[0x0d][col[1]] ^ AES.Gmul[0x09][col[2]] ^ AES.Gmul[0x0e][col[3]],
                    ))
        self.state = ss

    def cipher(self, block):
        #print "round[ 0].input: {0}".format(block.encode('hex'))
        n = self.nb * 4
        self.state = map(ord, block)
        keys = self.key_schedule()
        #print "round[ 0].k_sch: {0}".format(keys[0:n].encode('hex'))
        self.add_round_key(keys[0:n])
        for r in range(1, self.nr):
            #print "round[{0}].start: {1}".format(r,self.state.encode('hex'))
            self.sub_bytes()
            #print "round[{0}].s_box: {1}".format(r,self.state.encode('hex'))
            self.shift_rows()
            #print "round[{0}].s_row: {1}".format(r,self.state.encode('hex'))
            self.mix_columns()
            #print "round[{0}].m_col: {1}".format(r,self.state.encode('hex'))
            k = keys[r*n:(r+1)*n]
            #print "round[{0}].k_sch: {1}".format(r,k.encode('hex'))
            self.add_round_key(k)

        self.sub_bytes()
        self.shift_rows()
        self.add_round_key(keys[self.nr*n:])
        #print "output: {0}".format(self.state.encode('hex'))
        return "".join(map(chr, self.state))

    def inv_cipher(self, block):
        #print "round[ 0].iinput: {0}".format(block.encode('hex'))
        n = self.nb * 4
        self.state = map(ord, block)
        keys = self.key_schedule()
        k = keys[self.nr*n:(self.nr+1)*n]
        #print "round[ 0].ik_sch: {0}".format(k.encode('hex'))
        self.add_round_key(k)
        for r in range(self.nr-1, 0, -1):
            #print "round[{0}].istart: {1}".format(r,self.state.encode('hex'))
            self.inv_shift_rows()
            #print "round[{0}].is_row: {1}".format(r,self.state.encode('hex'))
            self.inv_sub_bytes()
            #print "round[{0}].is_box: {1}".format(r,self.state.encode('hex'))
            k = keys[r*n:(r+1)*n]
            #print "round[{0}].ik_sch: {1}".format(r,k.encode('hex'))
            self.add_round_key(k)
            #print "round[{0}].ik_add: {1}".format(r,self.state.encode('hex'))
            self.inv_mix_columns()
            #print "round[{0}].im_col: {1}".format(r,self.state.encode('hex'))

        self.inv_shift_rows()
        self.inv_sub_bytes()
        self.add_round_key(keys[0:n])
        #print "output: {0}".format(self.state.encode('hex'))
        return "".join(map(chr, self.state))



class AES_128(AES):
    def __init__(self):
        self.nb = 4
        self.nr = 10
        self.nk = 4

if __name__=="__main__":
    key = "2b7e151628aed2a6abf7158809cf4f3c".decode('hex')
    #key = "000102030405060708090a0b0c0d0e0f".decode('hex')
    check = (
            #("00112233445566778899aabbccddeeff", "69c4e0d86a7b0430d8cdb78070b4c55a"),
            ("6bc1bee22e409f96e93d7e117393172a", "3ad77bb40d7a3660a89ecaf32466ef97"),
            ("ae2d8a571e03ac9c9eb76fac45af8e51", "f5d3d58503b9699de785895a96fdbaaf"),
            ("30c81c46a35ce411e5fbc1191a0a52ef", "43b1cd7f598ece23881b00e3ed030688"),
            ("f69f2445df4f9b17ad2b417be66c3710", "7b0c785e27e8ad3f8223207104725dd4"),
            )
    crypt = AES_128()
    crypt.key = key
    for c in check:
        p = c[0].decode('hex')
        v = c[1].decode('hex')
        t = crypt.cipher(p)
        if t == v:
            print "yay!"
        else:
            print "{0} != {1}".format(t.encode('hex'), c[1])
        t = crypt.inv_cipher(v)
        if t == p:
            print "yay!"
        else:
            print "{0} != {1}".format(t.encode('hex'), c[1])

is this it ? does this code end with the else statement in lines 217-218 or is there something that I am overlooking?

This is not meant for executing, it is meant for importing and using the AES class

by any chance, do you have ported version of python3?

yeah, I really don't think much of this gist, its got some pretty weird stuff in the metaclass, which probably causes some python 2/3 issues. also, AES doesn't really make a great base class, you could determine if its AES 128, 192, and 256 by just measuring the size of an initialized key and setting the number of rounds appropriately. AES implies a block size of 128 bits.
basically its a ride on the fail boat. I think the OP was trying to look smart.