Cryptography
“There are two kinds of cryptography in this world: cryptography that will stop your kid sister from reading your files, and cryptography that will stop major governments from reading your files.”
Applied Cryptography 2nd edition Source Code in C
Published by John Wiley & Sons, 1996
BIP39/44 word list (2048 seed words)
https://github.com/bitcoin/bips/blob/master/bip-0039/english.txt
Enigma
Elliptical curves
Caesar cipher
Cryptographic seed