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pythonencryptionaesrsa
Chelsea-Fox
Chelsea-Fox

Reputation: 11

Python-rsa: can encrypt cannot decrypt

New rephrased Question

There are two programs that work together, a client and a server.

The client is having issues decrypting, and i have ran the following test on the client without any server interaction and this does not work.

I get rsa.pkcs1.DecryptionError: Decryption failed when i run this code on the client.

# Public key saved in ini file as this format "PublicKey(n, e)"
# Private key saved in ini file as this format "PrivateKey(n, e, d, p, q)"

key_string = public_key.strip("PublicKey(").strip(")")
n, e = key_string.split(", ", 1)
value = rsa.encrypt(b"Hello", public_key)

key_string = self.private_key.strip("PrivateKey(").strip(")")
n, e, d, p, q = key_string.split(", ", 4)
private_key = rsa.PrivateKey(int(n), int(e), int(d), int(p), int(q))
decrypted = rsa.decrypt(value, private_key)

Old "Question" asked

I am writing a python program that is essentially a P2P chat application utilising a rendezvous server for new connections.

Walkthrough of the steps taken by client/server.

Client:

  • Connects to server using sockets
  • Sends its public key to server

Server:

  • Reads public key
  • Creates AES key and ciphers a message (list of already connected peers)
  • Encrypts the AES Key using the clients RSA public key
  • Sends the key and ciphertext

Client:

  • Reads the information and splits into the key portion and the ciphertext portion
  • Decrypts the AES Key (However this fails even though the same code works on the server to decode)
  • Decrypts the cipher text using the now unencrypted AES Key

# Encrypt with AES cipher_text, key, nonce = self.aes.encrypt(json.dumps(message))
# Encrypt AES Key with RSA encrypted_key = self.rsa.encrypt(key, peer['public_key'])

# Send data to peer self.socket.sendto(encrypted_key + nonce + cipher_text, peer['address']) ```

``` CLIENT CODE

data, address = self.socket.recvfrom(65536) recv = {"key": data[:256],
"nonce": data[256:272], "data": data[272:]}

key = self.rsa.decrypt(recv["key"]) peers =
json.loads(self.aes.decrypt(recv["data"], key, recv["nonce"])) ```

Upvotes: 0

Views: 1378

Answers (1)

Chelsea-Fox
Chelsea-Fox

Reputation: 11

Solved this, Thanks for the help!

The error was with my import of the config file, my statement was checking if there was a valid RSA-pub/priv key and if there wasn't it would generate a new pair for the user.

The problem was it was always generating a new keypair. meaning it was attempting to decrypt with the incorrect private key.

Upvotes: 1

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