This questiоn is relаted tо the distributed systems security mоdules. Mаny secure services use https (аs you did in project 4) where a client C accesses a remote service S over an open network. For secure communication and authentication, services often have certificates but clients are not required to provide certificates when a secure channel is set up between C and S.Since a client certificate is not available, assume a secure channel is set up using the following protocol (this is a highly simplified version of the real protocol). C creates a secret key K and stores it locally. It also encrypts it with server S's public key and sends it to S, which uses its private key to retrieve K. Messages exchanged between C and S are encrypted with K. How is a secure channel that is authenticated and ensures confidentiality defined in the distributed systems security paper? (1+1 pts.) Is the channel established as above authenticated and does it provide confidentiality? (2+2 pts.) Service S provides access to files and a certain file F can be read by principal (Alice ∧ Bob). Consider the following cases and explain if Charlie will be able to gain read access to F. Explain your answer. Both Alice and Bob share their private keys with Charlie. ( 1+2 pts.) Alice creates a statement Alice says Charlie => Alice, and Bob creates a statement Bob says Charlie => Bob. They provide these statements to Charlie. (1 + 2 pts.) Alice and Bob both delegate to Charlie (e.g., Charlie has the credentials Charlie for Alice and Charlie for Bob. (1+ 2pts.) If Alice and Bob do not want to allow Charlie to have their full authority, which of the above three options must they choose? How will access to F be controlled based on the option you choose? (2 + 2 pts.) Assume we use the secure boot, secure communication channel and delegation protocols to build a secure distributed system where access control for a file at a file service can be specified for a remote user U. Assume U delegates to a node that is running a securely booted operating system OS on a machine M. Access to file F is governed with the access control statement "M as OS as Accounting for Alice can access file F". It has been discovered that there is a compromise and the data in F has been accessed by an attacker who is not authorized. An investigation of the compromise results in one of the findings listed below. Does each finding in cases I-III explain the unauthorized access? Explain your answer. The attacker has stolen M but Alice did logout of M as OS before this happened. (2+3 pts.) The attacker was able to compromise OS by exploiting a vulnerability while Alice was logged in but this happened well after Alice's login session was initiated. The compromise was immediately detected and M was securely rebooted with OS. (2+ 3 pts.) The attacker is able to phish Alice and steal her private key but she still has possession of M. (2 +1 pts.) Is the phishing attack described in 3.III feasible? Explain how it can be successfully launched or why it is not feasible. Explain your answer. (1+2 pts.)