Basic implementation of naive ElGamal cryptosystem.
# Help
$ python3.9 main.py -h
# Generate crypto keys
$ python3.9 main.py elgamal gen_keys <n_bits> <certainty> <pubkeys_file> <privkey_file>
# Encrypt file
$ python3.9 main.py elgamal gen_keys <pubkeys_file> <plaintext_file> <encrypted_file>
# Decrypt file
$ python3.9 main.py elgamal decrypt <pubkeys_file> <privkey_file> <encrypted_file> <decrypted_file>