What is your understanding of the difference between direct and arbitrated digital signature?

Write a paper that answers the numbered questions below. Be prepared to fully support your answers.
1. What are the properties a digital signature should have?
2. What is your understanding of the difference between direct and arbitrated digital signature?
3. What is your understanding of a suppress-replay attack?
Please make sure you follow APA format. I need the following in the paper.
1. Running head
2. Abstract
3. Introduction
4. Conclusions
5. References
Please use internet sources!