How can I encrypt/decrypt 12-digit decimal numbers to other ones, using a password and Java?

Question

I have already read Using Java to encrypt integers and Encrypting with DES Using a Pass Phrase.

All I need is a simple Encrypter which transforms a 12 digit number t

Answer 1

For mathematical reasons, most cyphers will produce "more" bytes (i.e. they will pad the input). So you will have to accept that the code generates 16bytes out of your 12 digit number.

When the string is decoded, you will get the 12 digit number back but during transport, you need 16 bytes.