In Python, there are many libraries using which one can perform RSA key generation, encryption, and decryption. Python rsa module is one such example. But, in this article, we would discuss how to use RSA keys to encrypt and decrypt text without using any cryptographic module. We would use some basic modules like secrets and math and use them to encrypt and decrypt texts using RSA keys.

We have already discussed how to generate a large random prime number in Python and how to use two large prime numbers to generate RSA keys. In this article, we would use the generated RSA keys to encrypt and decrypt texts.

But, before we discuss how to implement RSA encryption and decryption in Python, let’s try to understand how to encrypt and decrypt texts using the rsa module in Python.

import rsa

KEY_LENGTH = 2048
publickey, privatekey = rsa.newkeys(KEY_LENGTH)

plaintext = "Secret"

ciphertext = rsa.encrypt(plaintext.encode(), publickey)

decrypted_text = rsa.decrypt(ciphertext, privatekey).decode()
print(decrypted_text)

The very first thing we would notice is we use two methods encode() and decode() while encrypting and decrypting a text respectively. Let’s first try to understand why we do so.