4305.sagews

import binascii
bits=256 # Generate two large prime numbers
p = next_prime( ZZ.random_element(1, 2^(bits//2 +1)) ) 
q = next_prime( ZZ.random_element(1, 2^(bits//2 +1)) )
n = p*q

phi_n = (p - 1)*(q - 1)
while True:
   e = ZZ.random_element(1, phi_n)
   if gcd(e, phi_n) == 1: break
d = power_mod(e, -1, phi_n)  #computes e^(-1) mod phi_n
e,d,n

(18504618844489859274977983157852324676921577873264505513536994768681728090807, 4244270334285079821131998092697524738650529643354327055069383089061088156623, 22224140447341099545733723057734793861666674509228661146298555277781225356847)

m=int(binascii.hexlify('Test Message'),16)
c=power_mod(m,e,n)
c

9329205991968375512579524637518670290434882710412944984360355943848456393735

b=power_mod(c,d,n)
b

26119387547069534007986317157

binascii.unhexlify("%X" % b)

'Test Message'