[FIXED] Python and java AES/ECB/PKCS5 encryption

Issue

JAVA VERSION:

public class EncryptUtil {
    public static String AESEncode(String encodeRules, String content) {
        try {
            KeyGenerator keygen = KeyGenerator.getInstance("AES");
            keygen.init(128, new SecureRandom(encodeRules.getBytes()));
        SecretKey original_key = keygen.generateKey();
        byte[] raw = original_key.getEncoded();
        SecretKey key = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        byte[] byte_encode = content.getBytes("utf-8");
        byte[] byte_AES = cipher.doFinal(byte_encode);
        return new String(Base64.getEncoder().encode(byte_AES));
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        e.printStackTrace();
    } catch (InvalidKeyException e) {
        e.printStackTrace();
    } catch (IllegalBlockSizeException e) {
        e.printStackTrace();
    } catch (BadPaddingException e) {
        e.printStackTrace();
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }
       return null;
   }

}

When i run this code:

System.out.println(EncryptUtil.AESEncode("1234567812345678", python&java"));

I've got:

V5FFUgDi7VZaJ0qGzDISoA==

PYTHON VERSION:

import base64

from Crypto.Cipher import AES

BLOCK_SIZE = 16  # Bytes
pad = lambda s: s + (BLOCK_SIZE - len(s) % BLOCK_SIZE) * \
            chr(BLOCK_SIZE - len(s) % BLOCK_SIZE)
unpad = lambda s: s[:-ord(s[len(s) - 1:])]


class AESUtil:
    __BLOCK_SIZE_16 = BLOCK_SIZE_16 = AES.block_size

    def __init__(self, key):
         self.key = key

    def encrypt(self, raw):
        raw = pad(raw)
        cipher = AES.new(self.key, AES.MODE_ECB)
        return base64.b64encode(cipher.encrypt(raw))

    def decrypt(self, enc):
        enc = base64.b64decode(enc)
        cipher = AES.new(self.key, AES.MODE_ECB)
        return unpad(cipher.decrypt(enc))

I know java use AES/ECB/PKCS#5 by default, but when I run the encrypt method ：

cipher_text = AESUtil("1234567812345678").encryt('python&java')

got:b'3mjygpK1d7ThCRK98ssZhA=='

The pad and unpad i found them in Googles. How do I edit my PYTHON code make the cipher_text equals JAVA encryption. Can somebody know how to fix it?

Solution

You use different encryption keys

In Java

System.out.println(EncryptUtil.AESEncode("1234567812345678", "python&java"));

See the code:

KeyGenerator keygen = KeyGenerator.getInstance("AES");
keygen.init(128, new SecureRandom(encodeRules.getBytes()));
SecretKey original_key = keygen.generateKey();
byte[] raw = original_key.getEncoded();

If you print the raw key, you will get fd839759956ba4a47922e8ee7c902f52 (HEX encoded), that's the encryption key

If you would like to use the provided key directy, you should use

byte[] raw = encodeRules.getBytes(); 
// (assuming encodeRules has 16 bytes)

How do I edit my PYTHON code make the cipher_text equals JAVA encryption

That's tricky.. you may have a look how SecureRandom works, but IMHO it's easier to fix the Java implementation to create a key you expect

Regardless that I'd consider the implementation not secure enough - using ECB and simple key.

Answered By - gusto2
Answer Checked By - Katrina (JavaFixing Volunteer)