javax crypto IllegalBlockSizeException Input length must be multiple of 16 when decrypting with padded cipher

Question

I m getting a decrypting error in java class   javax crypto IllegalBlockSizeException        Input length must be multiple of 16 when decrypting with padded cipher    What can I do to solve this problem   UPDATE   I forgot to mention it is working once and when the second time im trying to execute it again its throwing the above mentioned error   package com tb module service  import java security Key  import java security spec InvalidKeySpecException   import javax crypto Cipher  import javax crypto spec SecretKeySpec   import sun misc            This class is used for encrypt and decrypt the  password field         public class PswdEnc        private static final String ALGO    AES       private static final byte   keyValue   new byte      T    h    e    B    e    s    t   S    e    c    r   e    t    K    e    y          public static String encrypt String Data  throws Exception           Key key   generateKey            Cipher c   Cipher getInstance ALGO           c init Cipher ENCRYPT MODE  key           byte   encVal   c doFinal Data getBytes             String encryptedValue   new BASE64Encoder   encode encVal           return encryptedValue             public static String decrypt String encryptedData  throws Exception           Key key   generateKey             Cipher c   Cipher getInstance ALGO           c init Cipher DECRYPT MODE  key           byte   decordedValue   new BASE64Decoder   decodeBuffer encryptedData           byte   decValue   c doFinal decordedValue           String decryptedValue   new String decValue           return decryptedValue              private static Key generateKey   throws Exception           Key key   new SecretKeySpec keyValue  ALGO           return key

User · Answer

Well that is Because of

you are only able to encrypt data in blocks of 128 bits or 16 bytes. That's why you are getting that IllegalBlockSizeException exception. and the one way is to encrypt that data Directly into the String.

look this. Try and u will be able to resolve this

public static String decrypt(String encryptedData) throws Exception {

    Key key = generateKey();
    Cipher c = Cipher.getInstance(ALGO);
    c.init(Cipher.DECRYPT_MODE, key);
    String decordedValue = new BASE64Decoder().decodeBuffer(encryptedData).toString().trim();
    System.out.println("This is Data to be Decrypted" + decordedValue);
    return decordedValue;
}

hope that will help.

User · Answer

A few comments   import sun misc    Don t do this   It is non-standard and not guaranteed to be the same between implementations   There are other libraries with Base64 conversion available   byte   encVal   c doFinal Data getBytes      You are relying on the default character encoding here   Always specify what character encoding you are using  byte   encVal   c doFinal Data getBytes  UTF-8      Defaults might be different in different places   As  thegrinner pointed out  you need to explicitly check the length of your byte arrays   If there is a discrepancy  then compare them byte by byte to see where the difference is creeping in

User · Answer

The algorithm you are using   AES   is a shorthand for  AES ECB NoPadding   What this means is that you are using the AES algorithm with 128-bit key size and block size  with the ECB mode of operation and no padding   In other words  you are only able to encrypt data in blocks of 128 bits or 16 bytes  That s why you are getting that IllegalBlockSizeException exception   If you want to encrypt data in sizes that are not multiple of 16 bytes  you are either going to have to use some kind of padding  or a cipher-stream  For instance  you could use CBC mode  a mode of operation that effectively transforms a block cipher into a stream cipher  by specifying  AES CBC NoPadding  as the algorithm  or PKCS5 padding by specifying  AES ECB PKCS5   which will automatically add some bytes at the end of your data in a very specific format to make the size of the ciphertext multiple of 16 bytes  and in a way that the decryption algorithm will understand that it has to ignore some data   In any case  I strongly suggest that you stop right now what you are doing and go study some very introductory material on cryptography  For instance  check Crypto I on Coursera  You should understand very well the implications of choosing one mode or another  what are their strengths and  most importantly  their weaknesses  Without this knowledge  it is very easy to build systems which are very easy to break     Update  based on your comments on the question  don t ever encrypt passwords when storing them at a database      You should never  ever do this  You must HASH the passwords  properly salted  which is completely different from encrypting  Really  please  don t do what you are trying to do    By encrypting the passwords  they can be decrypted  What this means is that you  as the database manager and who knows the secret key  you will be able to read every password stored in your database  Either you knew this and are doing something very  very bad  or you didn t know this  and should get shocked and stop it

[java] javax.crypto.IllegalBlockSizeException : Input length must be multiple of 16 when decrypting with padded cipher

Examples related to java

Examples related to encryption