CSE 551 -- Programming Assignment #3

Overview

For this assignment, you will implement a simple Web server that provides a simple "notary" service. You are allowed to start with the language of your choice, and take advantage of whatever support libraries you can find for that language. (Hint: perl, python, and ruby all have extensive HTTP and network libraries available that will massively simplify this programming assignment.) You may not start with a fully functioning web server such as Apache, however.

The notary service provides a simple interface:

• People visit a web page, upload a file through that web page to your Web server. Your Web server hashes the file, signs the concatenation of (hash + timestamp), and displays the signature on a result page.

• The server keeps track of all signatures that it has ever been asked to produce, and displays them on a different page for anyone to see. (Note: this implies you have to track those signatures across machine reboot.)

• The server displays its public key on a third page. (Note: this implies you need to generate a pub/priv keypair for your server, and keep track of them.)

Requirements

• You are free to use whatever hash and public key signature scheme you prefer, as long as they provide good crypotographic strength. If you pick a reasonable implementation language, chances are that the language has cryptography libraries available that implement these for you. I don't recommend implementing your own. ;)

• Your server must have a multi-process architecture: in other words, concurrent requests must be handled by concurrently running processes, rather than being serialized within a single process. (I really do mean process, not threads.) You can choose whether you fork a process for each request, or whether you use a process pool; The former is simpler to build. Both the signature generation and the reading/writing of network data should be handled by a separate process -- i.e., don't just hand off signature generation to a worker process, hand off both signatures and network reading/writing.

• Your server must take a command line argument that specifies what IP port it listens on.

• You must leave your server running for the remainder of the quarter. This implies that if your server crashes, or if the machine on which it is running crashes, you'll need to restart it. I recommend implementing a simple fault tolerance script, and having a program on some external machine monitor the server to let you know if you need to kick it. If you don't have access to your own machine, you can launch your server on attu.cs. (As usual, please be a good citizen and don't abuse attu.)

What to turn in

• a very short description of how you implemented your server -- its design, any pertinent implementation details, what choice of crypto you used, etc.

• the URLs I should use for the three webpages described in the "Overview" section above.

• your source code

• a "delivered bandwidth" vs. "latency" curve of the sort we discussed in class, for the file submission + hash generation web page.