Instructions: Show all work. No electronic devices are allowed. This exam is open book, open notes. You have 100 minutes to complete the exam.
Please prepare your answers on separate sheets of paper. You may write your answers on the sheet of paper with the question (front and back). If you need more space, please attach a separate sheet of paper to the page with the particular question. Do NOT extend your answer on the back of the sheet for a different question, and do NOT use the same extra sheet of paper to answer more than one question.
In particular, each numbered questions must appear on separate pieces of paper so that the exam can be split for grading. Be sure to include your name and USC ID number on each page.
There are 100 points in all and 4 questions.
Alice and Bob have each been asked to come up with individual key management solutions for digital signatures in their company.
Bob suggests that the company just use the conventional method for public key systems. That is, each employee / department uses their own key generation mechanism and stores the private key for their own use and stores the public key on a well known publicly accessible server.
Alice suggests that instead of putting employees public keys on a public server, all public keys of individuals and departments are stored only on a local server with access to only company employees. Only a single public key of the company would be made available on a public server and it would be signed by a third party for assuring the association to all outsiders. Whenever an outsider needs to communicate with an employee, they encrypt the message with company's public key. When it reaches the company's server, the server uses the internally available public key for the employee to encrypt the message further with this key. The employee has both private keys which can decrypt this double encrypted message.
For each of the systems and services listed below, explain which entities (people, processes, servers, hardware) are relied upon for the expected service to be provided securely and for the expected assurance (e.g. confidentiality, authentication, etc) to hold. For each subpart of this problem (3.1, 3.2, etc) give an example where the security is compromised if one of the trusted parties does not act in the way that it is supposed to act. Please note that in grading this question, your score will depend on how strong an example you provide - i.e. you may provide a correct example but might get full credit if there is a better one that you miss. There will, however, me multiple examples that can get full credit.
You have been hired by a consortium of online game facilitators to design the next generation security architecture for online games. A recent problem for gaming companies is the use of Phishing and malicious code to steal the identities of legitimate users, whose characters online wealth is then stolen and passed on to other characters.
Your first task is to advise the consortium on the design of an authentication system by which users will prove their identity (and hence the ownership of their online persona) when playing a game. The system you suggest should allow a user to prove his or her identity only when using legitimate, unmodified (i.e. no cheats) versions of the online game, and the approach should be resistant to attempts to steal a user's identity by malicious software such as viruses or bots that might have infected the user's computer.