Getting "EVP_DecryptFinal_ex: Invalid End Block Length" during decryption

Question

I followed this tutorial on encrypting and decrypting simple strings in android / java:

https://stackoverflow.com/questions/4319496/how-to-encrypt-and-decrypt-data-in-java I created a cryptography class:

public class Cryptography { public static SecretKey generateKey() throws NoSuchAlgorithmException { MessageDigest digest = MessageDigest.getInstance("SHA"); digest.update("BhLKTyLoP YroUsRQT".getBytes()); return new SecretKeySpec(digest.digest(), 0, 16, "AES"); } public static byte[] encrypt(String message, SecretKey key) throws NoSuchAlgorithmException, BadPaddingException, IllegalBlockSizeException, NoSuchPaddingException, InvalidKeyException, UnsupportedEncodingException { Cipher aes = Cipher.getInstance("AES/ECB/PKCS5Padding"); aes.init(Cipher.ENCRYPT_MODE, key); return aes.doFinal(message.getBytes()); } public static String decrypt(byte[] cipherText, SecretKey key) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException { Cipher aes = Cipher.getInstance("AES/ECB/PKCS5Padding"); aes.init(Cipher.DECRYPT_MODE, key); return new String(aes.doFinal(cipherText)); } } 

I managed to encrypt the method and gave me this:

 Encrypted username: [ B@52aff408 Encrypted password: [ B@52aff6d8 

However, when I use decrypt:

 SecretKey secret = Cryptography.generateKey(); Log.d("encryption", "Decrypted username: " + Cryptography.decrypt(encryptedUsername.getBytes(),secret) + " Decrypted password: " + Cryptography.decrypt(encyptedPassword.getBytes(),secret)); 

This gives me an error:

 03-25 15:22:23.461 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ java.lang.RuntimeException: error:0606506D:digital envelope routines:EVP_DecryptFinal_ex:wrong final block length 03-25 15:22:23.461 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at org.apache.harmony.xnet.provider.jsse.NativeCrypto.EVP_CipherFinal_ex(Native Method) 03-25 15:22:23.461 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at org.apache.harmony.xnet.provider.jsse.OpenSSLCipher.doFinalInternal(OpenSSLCipher.java:398) 03-25 15:22:23.461 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at org.apache.harmony.xnet.provider.jsse.OpenSSLCipher.engineDoFinal(OpenSSLCipher.java:434) 03-25 15:22:23.461 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at javax.crypto.Cipher.doFinal(Cipher.java:1111) 03-25 15:22:23.461 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at com.sblive.utils.Cryptography.decrypt(Cryptography.java:28) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at com.sblive.aufschoolbliz.GradeBookFragment$2.onClick(GradeBookFragment.java:99) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at android.view.View.performClick(View.java:4240) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at android.view.View$PerformClick.run(View.java:17721) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at android.os.Handler.handleCallback(Handler.java:730) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:92) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at android.os.Looper.loop(Looper.java:137) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5103) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at java.lang.reflect.Method.invokeNative(Native Method) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:525) 03-25 15:22:23.465 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 03-25 15:22:23.469 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 03-25 15:22:23.469 2073-2073/com.sblive.aufschoolbliz W/System.err﹕ at dalvik.system.NativeStart.main(Native Method) 

Answer 1

Encrypted Username: [B @ 52aff408

Encrypted Password: [B @ 52aff6d8

They are too small. Assuming the text message was less than 16 bytes, this should be exactly 16 bytes due to the PKCS addition.

You have an encoding problem. Probably an embedded zero that cuts off the end of the encryption text when interpreting the string ...

In fact, they look like typing pointers ....