One of the most basic philosophical questions stems from attempting to identify oneself, with the first step of proving you actually exist. René Descartes provides a proof with
Cogito ergo sum
meaning, “I think, therefore I am.” The intuition is that the mere fact of thinking forms a proof that you exist. But who or what are you exactly? What identifies you? How can we definitively prove you are what you claim to be? Who you claim to be? The problem of identity is an incredibly hard one—how do you know a letter in the mail is from the person that signed it? How do you know a text was written by the owner of a certain phone? How do you know an email comes from the person that owns an email address? This is a fundamental problem that faces the fields of computer science and cryptography, and it is incredibly hard to solve.