Message privacy is usually achieved through cryptography. This process involves using a key to insert a plain text message into an algorithm, which transforms the information into illegible text.

The receiver, with a proper key, can insert this cipher text back into a symmetric algorithm to recreate the original plain text message.

Only a person with the right key and algorithm can decrypt the message.

If someone other than the intended participant captures the data, he can see only cipher text, which is a bunch of meaningless characters.