0) High-level summary of the SPDZ malicious online protocol

1) Let's say $n$ parties hold *authenticated* additive shares of a value $a$. The parties want to compute the value $2a$, but the n-th player is malicious, and wants to change the result to be $2a + 100$.
  a) Explain in one sentence how the malicious SPDZ protocol prevents this. 
  b) Is any information about the value of $a$ leaked to the malicious party by the secure opening protocol? Why or why not? (Explain in one sentence.)

2) Install Docker *before class*, and check that your installation is working.
  a) Windows users: https://docs.docker.com/docker-for-windows/
  b) MacOS users: https://docs.docker.com/docker-for-mac/
  c) Ubuntu users: https://docs.docker.com/install/linux/docker-ce/ubuntu/
  c) Other Linux distros: Check your distro's repositories/wiki.