8.1-2 for 4 November

1. The difficult part was understanding the details of the second example and the proposition in 8.1. There were enough details that it didn't come at a first reading.

2. I think the idea of a hash function is interesting because of signatures and error checking. I also liked the idea of being strongly/ collision-free, since even though the function is not injective it is hard to find two elements that map to the same thing.