Converting a SecretKey

Question

Hi! can anyone help on how to convert a SecretKey format to an int then to String and back to int and String and lastly back to a SecretKey format?
And, how to encrypt and decrypt a string instead of a file?

Answer 1

A Key isn't an integer - it's a sequence of bytes, and it's often too big to fit into an int. Even if it does fit into one of the primitive types, in order to do things like encode it as a String and rebuild Key objects from it, you're going to want to treat it as a byte[].
You could use BigInteger to do your operations on the Key. Try something like this:Key myKey = .....;
byte[] myKeyBytes = myKey.getEncoded();
BigInteger myKeyAsInt = new BigInteger( myKeybytes );
// Do arithmetic on your key here
String myKeyBase64 = Base64.encode( myKeyAsInt.toByteArray() );
// send key elsewhere; upon receipt, do:
byte[] newBigIntBytes = Base64.decode(myKeyBase64);
BigInteger newKeyAsBigInt = new BigInteger(newBigIntBytes);
// undo your arithmetic here
byte[] newKeyBytes = newKeyAsBigInt.toByteArray();
EncodedKeySpec newKeySpec = new EncodedKeySpec(newKeyBytes);
Key myKey = KeyFactory.getInstance(myAlgorithm).generateSecret(newKeySpec);You need to fill in some blanks here, obviously - but this shows the approach. Note that "Base64" isn't a standard part of Java - do a web-search and you'l find a bunch of available implementations, tho.
Note that you need to be REALLY CAREFUL doing math on keys. If you do something that isn't reversible, there's no way to get your original key back.
Regarding this:
i got the key from the DES algorithm, so it's in HEX form right?No - it's a stream of bytes. You can print it in hex, if you like. In Java, it's an Object (a SecretKey), and you need to use getEncoded() to get it in byte[] form.
Good luck,
Grant