Digital signature
Computational thinking, problem-solving and programming[1]
A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents. A valid digital signature, where the prerequisites are satisfied, gives a recipient very strong reason to believe that the message was created by a known sender (authentication), and that the message was not altered in transit (integrity).[2]
Encryption
This is an excellent video. The part you will really want to pay attention to is at 4:36 into the video.