Java AES-128 encryption of 1 block (16 byte) returns 2 blocks(32 byte) as output -

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i'm using following code aes-128 encryption encode single block of 16 byte length of encoded value gives 2 blocks of 32 byte. missing something?

      plainenc = aes.encrypt("thisisapassword!");  
      import java.security.*;     import java.security.spec.invalidkeyspecexception;     import javax.crypto.*;     import sun.misc.*;      public class aes {           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 {             system.out.println("string length: " + (data.getbytes()).length); //length = 16             key key = generatekey();             cipher chiper = cipher.getinstance(algo);             chiper.init(cipher.encrypt_mode, key);             byte[] encval = chiper.dofinal(data.getbytes());             system.out.println("output length: " + encval.length); //length = 32             string encryptedvalue = new base64encoder().encode(encval);             return encryptedvalue;         }          public static string decrypt(string encrypteddata) throws exception {             key key = generatekey();             cipher chiper = cipher.getinstance(algo);             chiper.init(cipher.decrypt_mode, key);             byte[] decordedvalue = new base64decoder().decodebuffer(encrypteddata);             byte[] decvalue = chiper.dofinal(decordedvalue);             string decryptedvalue = new string(decvalue);             return decryptedvalue;         }         private static key generatekey() throws exception {             key key = new secretkeyspec(keyvalue, algo);             return key;     }  }

cipher.getinstance("aes") returns cipher uses pkcs #5 padding. padding added in cases – when plaintext multiple of block size, whole block of padding added.

specify intentions explicitly in cipher.getinstance() call avoid relying on defaults , potentially causing confusion:

cipher.getinstance("aes/ecb/nopadding");

you see using ecb mode, bad choice in situation.


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