Secure communication using asymmetric cryptography

secom.py

#!/usr/bin/env python

from pathlib import Path
from base64 import b64encode, b64decode

from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.primitives.serialization.ssh import (
    SSHPrivateKeyTypes,
    SSHPublicKeyTypes,
)


def encrypt(message: bytes) -> bytes:
    path: Path = Path('~/.ssh/id_rsa.pub').expanduser()
    with open(path, 'rb') as f:
        pubkey: SSHPublicKeyTypes = serialization.load_ssh_public_key(f.read())
    ciphertext: bytes = pubkey.encrypt(
        message,
        padding.OAEP(
            mgf=padding.MGF1(algorithm=hashes.SHA256()),
            algorithm=hashes.SHA256(),
            label=None
        )
    )
    c64: bytes = b64encode(ciphertext)
    return c64


def decrypt(c64: bytes) -> bytes:
    path: Path = Path('~/.ssh/id_rsa').expanduser()
    with open(path, 'rb') as f:
        privkey: SSHPrivateKeyTypes = serialization.load_ssh_private_key(
            f.read(),
            password=None,      # TODO
        )
    ciphertext: bytes = b64decode(c64)
    message: bytes = privkey.decrypt(
        ciphertext,
        padding.OAEP(
            mgf=padding.MGF1(algorithm=hashes.SHA256()),
            algorithm=hashes.SHA256(),
            label=None
        )
    )
    return message


def main():
    message: str = 'message'
    c64: bytes = encrypt(message.encode('utf-8'))
    decoded: bytes = decrypt(c64)
    print(f'message: {message}')
    print(f'encoded: {c64}')
    print('decoded:', decoded.decode('utf-8'))


if __name__ == '__main__':
    main()