Asymmetric Encryption Conceptually

https://en.wikibooks.org/wiki/Cryptography/A_Basic_Public_Key_Example

https://blog.vrypan.net/2013/08/28/public-key-cryptography-for-non-geeks/

http://www.muppetlabs.com/~breadbox/txt/rsa.html

https://www.gpg4win.org/doc/en/gpg4win-compendium_8.html

http://irtfweb.ifa.hawaii.edu/~lockhart/gpg/gpg-cs.html

There are some special functions that, though what they do is simple enough, and how they do what they do is utterly transparent, figuring out how to undo what they do is a diabolical task. Such a creature is a trapdoor function. Anyone can fall through a trapdoor, but only those who know where the hidden lever is can climb back out again.

Brian Raiter

http://chriskulbacki.com/captivating-cryptography-part-2

(terminology may be unreliable, transcription may be unreliable, but ideas seem clear otherwise)