Problem
1. The aim is to achieve confidentiality ("secret code") in an asymmetric encryption system. What type of key [A or B, private or public] the sender (A) must encrypt with in that case, and which key should the recipient (B) decrypt with? Give a reason for the answer!
2. The aim is to achieve authentication of the sender in an asymmetric encryption system. What kind of key [A or B, private or public] the sender (A) must in that case encrypt with, and what key must the recipient (B) decrypt with? Give a reason for the answer!
3. A special form of cross sum calculation is to use a hash function. What is the most important property that an imprint function must have?
4. Briefly explain how fingerprinting and asymmetric encryption can be used to give a plain text document (e.g. e-mail) a digital signature, in such a way that the document can still read by anyone.