java me - J2ME AES Decryption Error(org.bouncycastle.crypto.InvalidCipherTextException: pad block corrupted) -

i doing encryption , decryption using aes algorithm bouncy castle

my encryption , decryption works ok gives me error when plain text size bigger

even giving non decrypted data

public static boolean setencryptionkey(string keytext) {     byte[] keybytes = keytext.getbytes();      key = new keyparameter(keybytes);     engine = new aesfastengine();     cipher = new paddedbufferedblockcipher(engine);      return true; } 

encryption:

public static string encryptstring(string plaintext) {          byte[] plainarray = plaintext.getbytes();          cipher.init(true, key);         byte[] cipherbytes = new byte[cipher.getoutputsize(plainarray.length)];         int cipherlength = cipher.processbytes(plainarray, 0, plainarray.length, cipherbytes, 0);         cipher.dofinal(cipherbytes, cipherlength);         string cipherstring = new string(cipherbytes);         return cipherstring;     } 

decryption:

public static string decryptstring(string encryptedtext) {          byte[] cipherbytes = encryptedtext.getbytes();         cipher.init(false, key);         byte[] decryptedbytes = new byte[cipher.getoutputsize(cipherbytes.length)];         int decryptedlength = cipher.processbytes(cipherbytes, 0, cipherbytes.length, decryptedbytes, 0);         cipher.dofinal(decryptedbytes, decryptedlength);         string decryptedstring = new string(decryptedbytes);          int index = decryptedstring.indexof("\u0000");         if (index >= 0)         {             decryptedstring = decryptedstring.substring(0, index);         }         return decryptedstring;     } 

this decryption giving me following error

org.bouncycastle.crypto.invalidciphertextexception: pad block corrupted         @ org.bouncycastle.crypto.paddings.pkcs7padding.padcount(+30)         @ org.bouncycastle.crypto.paddings.paddedbufferedblockcipher.dofinal(+190)         @ com.newcrypto.decryptstring(newcrypto.java:103)         @ com.new_midlet.startapp(new_midlet.java:23)         @ javax.microedition.midlet.midletproxy.startapp(midletproxy.java:44)         @ com.sun.midp.midlet.scheduler.schedule(scheduler.java:375)         @ com.sun.midp.main.main.runlocalclass(main.java:477)         @ com.sun.midp.main.main.main(+80) 

what problem ?

the line

string cipherstring = new string(cipherbytes); 

is bug. cipherbytes byte array arbitrary values , cannot converted string using of java string decoders. should send/save cipher byte array. if must make string you'll have use encoder. base64 encoders used, base16 (hex). can use apache commons codec or favorite, harder base64 codec.