Implementing-cryptography-using-python

Chapter 8 ■ Cryptographic Applications and PKI 231
Constructing Simple Text Encryption and
Decryption with RSA Certificates
In the next code listing, we’ll use the RSA certificates we created in the previous
section to encrypt and decrypt a simple message: To be encrypted. The module
uses the RSA encryption protocol according to PKCS#1 OAEP, and the scheme
is more properly known as RSAES-OAEP. At the receiver side, decryption can
be done using the private part of the RSA key:
from Crypto.Cipher import PKCS1_OAEP
from Crypto.PublicKey import RSA
message = b'To be encrypted'
key = RSA.importKey(open('public_key.pem').read())
cipher = PKCS1_OAEP.new(key)
ciphertext = cipher.encrypt(message)
print (ciphertext)
key = RSA.importKey(open('private_key.pem').read())
cipher = PKCS1_OAEP.new(key)
plaintext = cipher.decrypt(ciphertext)
print (plaintext)
Figure 8.3 shows the results of the previous code. The message entered is “To
be encrypted.” You will see the RSA encrypted output followed by the decryption
back to plaintext.
Figure 8.3: RSA decrypt