javax.crypto.BadPaddingException: Given final block not properly padded error while decryption

Question

I am doing encryption and decryption of data as follows but getting error ``` protected Cipher aes_Gen_with_Key(byte[] key) { Cipher cipher=null; try { byte[] key_hash = (key).toString().getBytes("UTF-8"); key_hash = Arrays.copyOf(key_hash, 32); // use only first 256 bit SecretKeySpec secretKeySpec = new SecretKeySpec(key_hash, "AES"); cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec); } catch (Exception e) { System.out.println("Error Occured"); } return cipher; } protected Cipher aes_Dec_with_Key(byte[] key,byte[] iv) { Cipher cipher=null; try { byte[] key_hash = (key).toString().getBytes("UTF-8"); key_hash = Arrays.copyOf(key_hash, 32); // use only first 256 bit SecretKeySpec secretKeySpec = new SecretKeySpec(key_hash, "AES"); cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); cipher.init(Cipher.DECRYPT_MODE,secretKeySpec,new IvParameterSpec(iv)); } catch (Exception e) { System.out.println(e); } return cipher; } ``` With above 2 f…

Accepted Answer

The code you presented works just fine. The error must lie in the code you haven't shared with us (i.e. the code that actually uses the `Cipher` objects).

I wrote the code below to test your question code:

```
public static void main(String[] args) throws Exception {

Random random = new Random();
  byte[] key = new byte[32];
  random.nextBytes(key);

byte[] plaintext = new byte[100];
  random.nextBytes(plaintext);

Cipher enc = aes_Gen_with_Key(key);

byte[] ciphertext = enc.doFinal(plaintext);
  byte[] iv = enc.getIV();

Cipher dec = aes_Dec_with_Key(key, iv);

byte[] recoveredPlaintext = dec.doFinal(ciphertext);

System.out.println(Arrays.equals(plaintext, recoveredPlaintext));    
}
```

Note, I made your two methods static. You should do the same, as they don't use any instance variables.

javax.crypto.BadPaddingException: Given final block not properly padded error while decryption

Solution

Problem