CODEWITHSUNDEEP
javapythonsocketsencryptionrsa
blazedosan002
blazedosan002

Reputation: 15

RSA Python Encrypt Message From Imported Java Public Key

I imported a public key from java to python i am using sockets

in java i am using RSA/ECB/PKCS1Padding

and in python i am using the Crypto library

in the variable server_public_key i'm importing the public key

and in cipher i use PKCS1_OAEP to encrypt the message

in ciphertext i encrypt the message

then i convert it to a bytearray

and then i sent it back to java

but java sends this error Exception in thread "main" javax.crypto.BadPaddingException: Decryption error

here's my code

message = "SENDING TO JAVA"
s= socket.socket()
     s.connect((address,9000))
        data = s.recv(1024)
        data = data[2:]
        server_public_key = RSA.importKey(data)
        cipher = PKCS1_OAEP.new(server_public_key)
        ciphertext = cipher.encrypt(mensaje)
        b = bytearray()
        b.extend(ciphertext)
        b = bytearray()
        b.extend(ciphertext)
        s.sendall(b)

Upvotes: 0

Views: 645

Answers (1)

President James K. Polk
President James K. Polk

Reputation: 42009

When I remove the inexplicable second copy of the ciphertext being sent, and clean up and correct the python code, it works for me. Here is the python code I used.

import socket
import struct

from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP

#
# the following is an alternative recvall function that can be used
# if your platform does not provide the MSG_WAITALL socket flag.
# 
def recvall2(s, size):
    received_chunks = []
    buf_size = 4096
    remaining = size
    while remaining > 0:
        received = s.recv(min(remaining, buf_size))
        if not received:
            raise Exception('unexcepted EOF')
        received_chunks.append(received)
        remaining -= len(received)
    return b''.join(received_chunks)

def recvall(s, size):
    return s.recv(size, socket.MSG_WAITALL)

def oaep_example():
    message = b"SENDING TO JAVA"
    s = socket.socket()
    s.connect(('127.0.0.1', 9000))
    pubkey_size = struct.unpack(">H", recvall(s, 2))[0]
    pubkey_der = recvall(s, pubkey_size)
    server_public_key = RSA.importKey(pubkey_der)
    cipher = PKCS1_OAEP.new(server_public_key)
    cipher_text = cipher.encrypt(message)
    s.sendall(cipher_text)
    s.close()

if __name__ == '__main__':
    oaep_example()

and the little Java server to demonstrate this is 

import com.google.common.io.ByteStreams;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.security.KeyPair;
import java.security.KeyPairGenerator;

public class Main {

    public static void main(String[] args) throws Exception {
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
        kpg.initialize(1024);
        KeyPair rsaKeyPair = kpg.generateKeyPair();
        ServerSocket serverSocket = new ServerSocket(9000);
        Socket socket = serverSocket.accept();
        DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
        byte[] encodedPubKey = rsaKeyPair.getPublic().getEncoded();
        dos.writeShort(encodedPubKey.length);
        dos.write(encodedPubKey);
        byte[] cipher = ByteStreams.toByteArray(socket.getInputStream());
        socket.close();
        Cipher c = Cipher.getInstance("RSA/ECB/OAEPWithSHA-1AndMGF1Padding");
        c.init(Cipher.DECRYPT_MODE, rsaKeyPair.getPrivate());
        byte[] plain = c.doFinal(cipher);
        System.out.println(new String(plain, StandardCharsets.UTF_8));
    }
}

Note: ByteStreams comes from the google Guava library.

Upvotes: 1

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