create a system that digitally signs (encryption) a document/message, Verifies(decryption) that document

Implementation of Digital Signature on Separate Systems. (I posted this earlier but I didn't check the pricing range and I made mistake by going with the default and I'm sorry for anyone that has already bid on it with that budget range but I can't pay what I don't have. I'm just a student in a 3rd world country) There are two main components of the system, 1. the encryption/signing component(system) which signs and encrypts a message or file (video, audio, graphic). It's a separate system on its own and has its own interface that enables the user to write a message and upload a file to digitally sign. 2. the decryption/verification part of the system, also a separate system on its own and that allows the user to decrypt and verify(validate) that the document has not been tempered with. also has an applet GUI. 3. there is also the need for a third component to the system, the compression algorithm; this is for the audio and video files that may be too heavy, this is why we need a compression algorithm that compresses the files before signing. 1 and 2 must be in java and made as straight-forward as possible. the GUI should also be simple to navigate . 3-compression is just an algorithm that shows how the compression is done. Most of the java codes for the digital signature are online but are not in applet form. the GUI for the Signer is included, its the same for the verifier. There is no need for the compression and decompression buttons since the compression is going to be on a separate algorithm. the system should be able to sign a file as well as the message written on the message box.