email big file

The actual question is:
] Suppose that you are responsible for the IT department of a university with the students around the world. It is infeasible to meet each of the students in person. The IT department is responsible for all secured communication with the students. Assume that there is a trusted certificate authority which can securely issue certificates to all involved parties. Please explain how you will achieve the following operations:

At the end of the semester, your department issues the academic transcript to individual students. How would you transmit Kim’s transcript to him/her via the Internet, which is not a secure communication channel. Assume that the transcript comes with scanned documents, and total size of the file is very big.

I would appreciate if you can tell me how would you send a big file along with attachments through unsecured channel . Because there is a limit on size of file that can be sent. So here we have such a file size which bigger than that max file size that can be sent. How would you send such a file ?

Suppose that you are responsible for the IT department of a university with the students around the world. It is infeasible to meet each of the students in person. The IT department is responsible for all secured communication with the students. Assume that there is a trusted certificate authority which can securely issue certificates to all involved parties. Please explain how you will achieve the following operations:

4.1. Kim is a new student and needs a password to access the university IT systems. How would you transmit the password to him/her through the Internet, which is not a secure communication channel.
4.2. At the end of the semester, your department issues the academic transcript to individual students. How would you transmit Kim’s transcript to him/her via the Internet, which is not a secure communication channel. Assume that the transcript comes with scanned documents, and total size of the file is very big.
4.3. From time to time, your department, on behalf of the University, makes public announcements. The announcements are of public accessible nature and can be shared and transmitted by any interested parties, say, prospective students. How would you guarantee the authenticity of your announcements?

For 4.2 and 4.3 ?