dotpaw podcast - Cryptography -

Cryptography is the process of hiding or coding information so that only the person a message was intended for can read it. The art of cryptography has been used to code messages for thousands of years and continues to be used in bank cards, computer passwords, and e-commerce.
The study of cryptography dates back to ancient Egypt, some 4,000 years ago, and is evident in their very complex pictograms, or hieroglyphics. The very first use of modern cryptography and ciphers still used today is attributed to Julius Caesar, a Roman general and politician.

He distrusted messengers and went to great lengths to conceal the communications with his officers and governors. The fear of important secrets leaking to the wrong people led to the development of a system where every character in his message was replaced by a letter three places ahead in the Roman alphabet.

https://www.cryptography101.org/

https://www.cs.cornell.edu/courses/cs5430/2021fa/TL01.introduction.html

https://www.openpgp.org/