I have python and android code for AES encryption. When I encrypt a text in android, it decrypt on python successfully but it can’t decrypt in android side. Do anyone have an idea?
Python code :
import base64
import hashlib
from Crypto import Random
from Crypto.Cipher import AES
class AESCipher:
def __init__(self, key):
self.bs = 16
self.key = hashlib.sha256(key.encode()).digest()
def encrypt(self, message):
message = self._pad(message)
iv = Random.new().read(AES.block_size)
cipher = AES.new(self.key, AES.MODE_CBC, iv)
return base64.b64encode(iv + cipher.encrypt(message)).decode('utf-8')
def decrypt(self, enc):
enc = base64.b64decode(enc)
iv = enc[:AES.block_size]
cipher = AES.new(self.key, AES.MODE_CBC, iv)
return self._unpad(cipher.decrypt(enc[AES.block_size:])).decode('utf-8')
def _pad(self, s):
return s + (self.bs - len(s) % self.bs) * chr(self.bs - len(s) % self.bs)
@staticmethod
def _unpad(s):
return s[:-ord(s[len(s)-1:])]
Android Code:
import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.util.Arrays;
import android.annotation.SuppressLint;
import android.location.Criteria;
import android.util.Base64;
import android.util.Log;
@SuppressLint("NewApi")
public class Crypt {
private static final String tag = Crypt.class.getSimpleName();
private static final String characterEncoding = "UTF-8";
private static final String cipherTransformation = "AES/CBC/PKCS5Padding";
private static final String aesEncryptionAlgorithm = "AES";
private static final String key = "this is my key";
private static byte[] ivBytes = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
private static byte[] keyBytes;
private static Crypt instance = null;
Crypt()
{
SecureRandom random = new SecureRandom();
Crypt.ivBytes = new byte[16];
random.nextBytes(Crypt.ivBytes);
}
public static Crypt getInstance() {
if(instance == null){
instance = new Crypt();
}
return instance;
}
public String encrypt_string(final String plain) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, IOException
{
return Base64.encodeToString(encrypt(plain.getBytes()), Base64.DEFAULT);
}
public String decrypt_string(final String plain) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, ClassNotFoundException, IOException
{
byte[] encryptedBytes = decrypt(Base64.decode(plain, 0));
return Base64.encodeToString( encryptedBytes, Base64.DEFAULT);
}
public byte[] encrypt( byte[] mes)
throws NoSuchAlgorithmException,
NoSuchPaddingException,
InvalidKeyException,
InvalidAlgorithmParameterException,
IllegalBlockSizeException,
BadPaddingException, IOException {
keyBytes = key.getBytes("UTF-8");
Log.d(tag,"Long KEY: "+keyBytes.length);
MessageDigest md = MessageDigest.getInstance("SHA-256");
md.update(keyBytes);
keyBytes = md.digest();
Log.d(tag,"Long KEY: "+keyBytes.length);
AlgorithmParameterSpec ivSpec = new IvParameterSpec(ivBytes);
SecretKeySpec newKey = new SecretKeySpec(keyBytes, aesEncryptionAlgorithm);
Cipher cipher = null;
cipher = Cipher.getInstance(cipherTransformation);
SecureRandom random = new SecureRandom();
Crypt.ivBytes = new byte[16];
random.nextBytes(Crypt.ivBytes);
cipher.init(Cipher.ENCRYPT_MODE, newKey, random);
// cipher.init(Cipher.ENCRYPT_MODE, newKey, ivSpec);
byte[] destination = new byte[ivBytes.length + mes.length];
System.arraycopy(ivBytes, 0, destination, 0, ivBytes.length);
System.arraycopy(mes, 0, destination, ivBytes.length, mes.length);
return cipher.doFinal(destination);
}
public byte[] decrypt( byte[] bytes)
throws NoSuchAlgorithmException,
NoSuchPaddingException,
InvalidKeyException,
InvalidAlgorithmParameterException,
IllegalBlockSizeException,
BadPaddingException, IOException, ClassNotFoundException {
keyBytes = key.getBytes("UTF-8");
Log.d(tag,"Long KEY: "+keyBytes.length);
MessageDigest md = MessageDigest.getInstance("SHA-256");
md.update(keyBytes);
keyBytes = md.digest();
Log.d(tag,"Long KEY: "+keyBytes.length);
byte[] ivB = Arrays.copyOfRange(bytes,0,16);
Log.d(tag, "IV: "+new String(ivB));
byte[] codB = Arrays.copyOfRange(bytes,16,bytes.length);
AlgorithmParameterSpec ivSpec = new IvParameterSpec(ivB);
SecretKeySpec newKey = new SecretKeySpec(keyBytes, aesEncryptionAlgorithm);
Cipher cipher = Cipher.getInstance(cipherTransformation);
cipher.init(Cipher.DECRYPT_MODE, newKey, ivSpec);
byte[] res = cipher.doFinal(codB);
return res;
}
}
When I ran this code on android:
String str = "this is local test";
Log.i("myTag", "step1: " + str);
String a = aesCrypt.encrypt_string(str);
Log.i("myTag", "step2: " + a);
String b = aesCrypt.decrypt_string(a);
Log.i("myTag", "step3: " + b);
Then I got this answer:
step1: this is local test
step2: a0F8MhzkSpRlM+aM1MKzUdVCoXIE5y5hh4PRuwPfAhofKwLJjTUbBvmJzTsKJDqF
step3: dGhpcyBpcyBsb2NhbCB0ZXN0
Do anyone have idea why it happens ?
You're encoding the output after decryption.
public String decrypt_string(final String plain) throws ...
{
byte[] encryptedBytes = decrypt(Base64.decode(plain, 0));
return Base64.encodeToString( encryptedBytes, Base64.DEFAULT);
// ^--------------------| this
}
If you only encrypt printable data then you can safely remove the Base64.encodeToString
call from the above code. To return the correct type, you can do
return new String(encryptedBytes);
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