unauthorized party can read the private key without the secret passphrase. Please note that while writing the keys to files, we are writing binary data. So, the files need to be opened in “wb” mode.

Next, we would import the exported keys from the corresponding files. The following piece of code can be used for that purpose.

def import_private_key(filename):

    with open(filename, "rb") as file:
        private_key = RSA.importKey(file.read(), 'MyPassphrase')

    return private_key


def import_public_key(filename):

    with open(filename, "rb") as file:
        public_key1 = RSA.importKey(file.read())

    return public_key1

Here also, we are reading binary data. So, the files need to be opened in “rb” mode. Please note that we used a passphrase while exporting the private key. So, we would need to use the same passphrase while reading the private key from the file.

The complete code for exporting and importing RSA keys is given below:

from Crypto.PublicKey import RSA


def export_private_key(private_key, filename):

    with open(filename, "wb") as file:
        file.write(private_key.exportKey('PEM', 'MyPassphrase'))
        file.close()


def export_public_key(public_key1, filename):

    with open(filename, "wb") as file:
        file.write(public_key1.exportKey('PEM'))
        file.close()


def import_private_key(filename):

    with open(filename, "rb") as file:
        private_key = RSA.importKey(file.read(), 'MyPassphrase')

    return private_key


def import_public_key(filename):

    with open(filename, "rb") as file:
        public_key1 = RSA.importKey(file.read())

    return public_key1


keypair = RSA.generate(2048)
public_key = keypair.publickey()

export_private_key(keypair, 'private_key.pem')
export_public_key(public_key, 'public_key.pem')

keypair = import_private_key('private_key.pem')
public_key = import_public_key('public_key.pem')

Now, we can use the imported keys for encryption and decryption. Interested readers, who want to know more on how to encrypt and decrypt data using the RSA module of PyCryptodome in Python can refer to this article: How to encrypt and decrypt data using the RSA module of PyCryptodome in Python?

I hope this helps. However, readers who want to know more about how different cryptographic algorithms work and how they are used in various secure network protocols can refer to the book “Cryptography And Public Key Infrastructure.”