RSA Encryption

#!/usr/bin/env python

''' Convert to and from ASCII text.
'''
def str_to_ascii(s):
    return [ord(c) for c in s]

def ascii_to_str(l):
    return ''.join(chr(x) for x in l)

''' Define math operations.
'''
def pow(x, n):
    r = x
    for i in range(n-1):
        r = r * x
    return r

def egcd(a, b):
    x,y, u,v = 0,1, 1,0
    while a != 0:
        q, r = b//a, b%a
        m, n = x-u*q, y-v*q
        b,a, x,y, u,v = a,r, u,v, m,n
    gcd = b
    return gcd, x, y

def modinv(a, m):
    gcd, x, y = egcd(a, m)
    if gcd != 1:
        return None
    else:
        return x % m

''' RSA encryption/decryption class.
'''
class RSA(object):
    _e, _d = 0, 0
    def __init__(self, p, q, e=1):
        self.p, self.q = p, q
        self.n = p * q
        self.m = (p-1) * (q-1)
        self.e = e
    @property
    def e(self):
        return self._e
    @e.setter
    def e(self, val):
        self._e = val
        self._d = modinv(self.e, self.m)
    @property
    def d(self):
        return self._d
    def encrypt(self, M):
        def _encrypt(_m, _e, _n):
            return int(pow(_m, _e) % _n)
        return [_encrypt(m, self.e, self.n) for m in M]
    def decrypt(self, C):
        def _decrypt(_c, _d, _n):
            return int(pow(_c, _d) % _n)
        return [_decrypt(c, self.d, self.n) for c in C]

if __name__ == '__main__':
    r = RSA(19, 11, 13)
    plaintext = 'My name is Ryan! What is your name?'
    M = str_to_ascii(plaintext)
    print 'M =', M
    C = r.encrypt(M)
    print 'C =', C
    M1 = r.decrypt(C)
    output = ascii_to_str(M1)
    print plaintext, '==', output, '?=', plaintext == output