RSA- BIgInteger Issue

Question

I want to use RSA algorithm, for encrypt and decrypt messages. Now, as RSA can encrypt and decrypt Big-integer (or Integer) value, I need the message as Big-integer value. Now, message can contain strings like "ABC 123". What can I do ? Any help or suggestion ?

Answer 1

If your message is initially ascii, you can use something like:

BigInteger i = new BigInteger();
While(j < msg.length() ) {
  i += ((byte)msg.charAt(j) << (j*7));
}

For working code consult the actual JavaDocs. But basically you just want to turn your bytes or chars into a number, so the idea is you just concatenate the bits together.

Answer 2

It can be done, by using

byte[] b = message.getBytes()
BigInteger = new BigInteger (b)