Introduction to the coursework

Throughout the module, you will be working on an extended coursework. The coursework is set out in 4 assignments:

(1) Cryptographic Hash Functions

(2) Transactions and Verification

(3) The Blockchain

(4) Adding new blocks: mining and the consensus mechanism

The first two assignments will be submitted together as coursework  1; the second two will be submitted as coursework 2.

Each of the coursework assignments involves two tasks: a programming task and a reflective essay on a related topic. In recognition that your background and interest will lead you to engage with the module in the most appropriate way for you, we are allowing you to choose your assessment route. You can choose, for each assignment, whether you want the ratio of programming/writing marks for the assignment to be 70/30; 50/50; or 30/70.

If you complete all the programming tasks, you will have implemented a new cryptocurrency and the blockchain that supports it. You will also compete to mine the most coins. You can do this thing!

Assignment 1: Cryptographic Hash Functions

This first assignment involves exploring an early cryptographic hash function, calledMD2. ‘MD’ stands for Message Digest. MD2 was designed by Ron Rivest, the ‘R’ of RSA.

The name, digest, refers to the idea that you can use the output of a hash function as a digest of the input. That is, you can use it as a kind of a compact description that acts as a proxy for the original thing being hashed.

MD2 is no longer usable as a cryptographic hash function: it has been broken. Part of the coursework involves exploring what that means. As technologies improve, it is harder for any function to be secure

We will not be using MD2 in our blockchain development. We will be using the more secure SHA256. You may have already had a feel for how we can work with SHA256 from one of the activities in this topic. SHA256 is the hash function used in Bitcoin. One of the ways it is more secure that MD2 is that the hashes are longer. SHA256 hashes are 256 bits long, as the name suggests. MD2 hashes are not 2 bits long as they would be if we were following the same naming convention. They are 128 bits long. Which is still pretty long. The name MD2 represents that it is the second hash function in the MD family. I think MD5 is the latest.

We are asking you to work on MD2 here because SHA256 is just too complicated to ask you to implement. The intrepid among you, may wish to give it a go! You can find a description at the following link: SHA256.

Programming Assignment 1

You are to implement MD2 in Python. I hope that by doing this you will get a sense of how these functions work. The main thing to understand as that they are completely deterministic and fairly easy to compute, all kinds of weird stuff are put in just to make it hard to undo.

Obfuscation is your goal. I have provided several kinds of description of MD2:

CW1Paper 1 Pseudo-code specification
CW1Paper 2: C Implementation
CW1Paper 3: A research paper that has a description