Base64

from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP
from Crypto.Signature import pkcs1_15
from Crypto.Hash import SHA256


def generate_keypair(bits=2048):
    """Generate an RSA public/private key pair."""
    key = RSA.generate(bits)
    return key


def encrypt(plaintext, public_key):
    """Encrypt data with RSA-OAEP."""
    cipher = PKCS1_OAEP.new(public_key)
    data = plaintext.encode() if isinstance(plaintext, str) else plaintext
    return cipher.encrypt(data)


def decrypt(ciphertext, private_key):
    """Decrypt data with RSA-OAEP."""
    cipher = PKCS1_OAEP.new(private_key)
    return cipher.decrypt(ciphertext).decode()


def sign(data, private_key):
    """Sign data with RSA-PSS + SHA-256."""
    h = SHA256.new(data.encode() if isinstance(data, str) else data)
    return pkcs1_15.new(private_key).sign(h)


def verify(data, signature, public_key):
    """Verify an RSA-PSS + SHA-256 signature."""
    h = SHA256.new(data.encode() if isinstance(data, str) else data)
    try:
        pkcs1_15.new(public_key).verify(h, signature)
        return True
    except (ValueError, TypeError):
        return False


if __name__ == '__main__':
    key = generate_keypair(2048)
    private_key = key
    public_key = key.publickey()

    # --- Encryption / Decryption ---
    message = "This is a secret message"
    ciphertext = encrypt(message, public_key)
    plaintext = decrypt(ciphertext, private_key)
    print("Original:  '%s'" % message)
    print("Decrypted: '%s'" % plaintext)

    # --- Signing / Verification ---
    data = "This data needs signing"
    signature = sign(data, private_key)
    verified = verify(data, signature, public_key)
    print("Signature verified: %s" % verified)

Practical RSA key generation, encryption, decryption, and digital signing in Python using PyCryptodome.

Red Links

• RSA
• GPG
• SHA
• Diffie-Hellman Key Exchange
• Password Hashing
• TLS
• One Time Pad
• HMAC
• Base64
• Elliptic Curve Cryptography