Encrypt/Decrypt message using PGPy

Question

I am trying out PGPy and I get an error whenever I encrypt or decrypt a message.

These are the codes that I use. Documentation and examples can be found here

Code to encrypt a message using the public key:

import pgpy

key_pub = '''BEGIN PUBLIC KEY BLOCK...END PUBLIC KEY BLOCK'''.lstrip()
message = "It worked!"

# import ASCII formatted public key
pub_key = pgpy.PGPKey()
pub_key.parse(key_pub)

# create new message
text_message = pgpy.PGPMessage.new(message)

# encrypt a message using pub key
encrypted_message = pub_key.encrypt(text_message)

print(encrypted_message)

This one gave the output but with a message

UserWarning: Selected compression algorithm not in key preferences
  encrypted_message = pub_key.encrypt(text_message)

which I don't get why.
Code to decrypt the message using the priv key:

import pgpy

key_priv ='''*BEGIN PRIV KEY BLOCK...END PRIV KEY BLOCK'''.lstrip()
cipher_text = '''BEGIN PGP MESSAGE...END PGP MESSAGE'''.lstrip()

# import ASCII formatted private key
priv_key = pgpy.PGPKey()
priv_key.parse(key_priv)

message_from_blob = pgpy.PGPMessage.from_blob(cipher_text)

# decrypts a message using priv key
decrypted_message = priv_key.decrypt(cipher_text)

print(decrypted_message)

And this one does not work at all.This is the error I get.

    Traceback (most recent call last):
  File "C:/Users..practice.py", line 13, in <module>
    decrypted_message = priv_key.decrypt(cipher_text)
  File "C:\Users...venv\lib\site-packages\pgpy\decorators.py", line 126, in _action
    self.check_attributes(key)
  File "C:\Users...venv\lib\site-packages\pgpy\decorators.py", line 111, in check_attributes
    raise PGPError("Expected: {attr:s} == {eval:s}. Got: {got:s}"
pgpy.errors.PGPError: Expected: is_unlocked == True. Got: False

Answer 1

1. Assuming that you have an RSA public and private key, encrypting a string or file can be done simply:

    PUBLIC_KEY_FILE = 'path/to/keyfile/my_pub_key.asc'    
    pub_key, _ = pgpy.PGPKey.from_file(str(PUBLIC_KEY_FILE))
    
    # Encrypt string
    txt_msg = pgpy.PGPMessage.new("Hello PGPy World")
    print('txt_msg.is_encrypted')
    print(txt_msg.is_encrypted)
    print('txt_msg.message')
    print(txt_msg.message)
    encrypted_txt_msg = pub_key.encrypt(txt_msg)
    print('encrypted_txt_msg.is_encrypted')
    print(encrypted_txt_msg.is_encrypted)
    print('encrypted_txt_msg.message')
    print(encrypted_txt_msg.message)
    
    # Encrypt file
    f_t_e = pgpy.PGPMessage.new(str(FILE_TO_ENCRYPT),file=True)
    print('f_t_e.is_encrypted')
    print(f_t_e.is_encrypted)
    encrypted_f_t_e = pub_key.encrypt(f_t_e)
    print('encrypted_f_t_e.is_encoded')
    print(encrypted_f_t_e.is_encrypted)

2. Assuming you have the RSA private key associated with the above public key (in the recipient list) and a text file containing the passphrase, decrypting a string or file is quite straightforward:

    # Load passphrase from file
    with open(PASSPHRASE_FILE,'r') as ppfp:
        PASSPHRASE = ppfp.readline().replace('\n','')
    print(PASSPHRASE)
    
    # Load private key
    PRIVATE_KEY_FILE='path/to/keyfile/my_prv_key.gpg'
    prv_key, _ = pgpy.PGPKey.from_file(str(PRIVATE_KEY_FILE))

    # Unlock private key
    print(prv_key.is_protected)  # Should be True
    with prv_key.unlock(PASSPHRASE):
        print(prv_key.is_unlocked)  #Should be True

        # Decrypt string
        decrypted_txt_msg = prv_key.decrypt(encrypted_txt_msg)
        print('decrypted_txt_msg.is_encrypted')
        print(decrypted_txt_msg.is_encrypted)
        print('decrypted_txt_msg.message')
        print(decrypted_txt_msg.message)

        # Decrypt file
        decrypted_f_t_e = prv_key.decrypt(encrypted_f_t_e)
        print('decrypted_f_t_e.is_encrypted')
        print(decrypted_f_t_e.is_encrypted)