Problem Generating 64 bit DES key

Posted on 2001-07-19
Medium Priority
Last Modified: 2010-08-05
I am using java's cryptography packages and using SunJCE as the security provider.  I am trying to create a 64 bit DES key.  I am getting the following error:

java.security.InvalidParameterException: Wrong keysize: must be equal to 56

Here is the code I am using:

Provider sunJCE = new com.sun.crypto.provider.SunJCE();

KeyGenerator generator = KeyGenerator.getInstance("DES");

generator.init(64, new SecureRandom());
Key key = generator.generateKey();
System.out.println("Generating DES Key... done");

ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(args[0]));

System.out.println("DES Key is saved to file" + args[0]);

When I changed 64 to 56, the key was generated correctly but I need a 64 bit key.  Any ideas?  Thanks.
Question by:paulca

Expert Comment

ID: 6300035

I think if you remove the 64 and just have
generator.init(new SecureRandom())
you don't have to specify the key size.  I did the following and it worked fine:

KeyGenerator keyGenerator = KeyGenerator.getInstance("DES");
      keyGenerator.init(new SecureRandom());
      SecretKey ourSecretKey = keyGenerator.generateKey();
      SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
      Class spec = Class.forName("javax.crypto.spec.DESKeySpec");
      DESKeySpec ks = (DESKeySpec)skf.getKeySpec(ourSecretKey,spec);
      // set ksBytes

      // encrypt a dummy string in order to generate an init vector
      Cipher newCipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
      newCipher.init(Cipher.ENCRYPT_MODE, ourSecretKey);
      // get initialization vector
      byte[] initVector = newCipher.getIV();

Accepted Solution

barrel earned 300 total points
ID: 6301310
A 56 bit DES key is in fact a 64 bit key, the 8 bits "missing" are filled with Dummy values.

The reason for needing 64 bits for the encryption algorithm is obvious, the reason why only 56 can be entered is because of the Wassenaar Arrangement which lists encryption as militairy property/technology (or something like that). Any (well.. not any) symmetric encryption algorithm may only use 56 bits keys.

For more information:


The encryption algortihm will thus fill the 56 bits with 8 dummy bits, giving 8 blocks of 8 bits. This is your 64 bits encryption

Hope this helps

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