olemus
krüptoalgoritm, mis asendab avateksti üksused (märgid, märgipaarid, märgikolmikud vms) krüptogrammiüksustega, mis võetakse samast, muust või mitmest märgistikust

Wiktionary:
(cryptography) A method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing an inverse substitution.

https://duckduckgo.com/?q=substitution+cipher&t=h_&iax=images&ia=images

näiteid
- Caesari šiffer https://en.wikipedia.org/wiki/Caesar_cipher
- ühekordne šifriplokk
- S-teisendus
- SP-teisendus

ülevaateid
https://techdifferences.com/difference-between-substitution-technique-and-transposition-technique.html

https://en.wikipedia.org/wiki/Substitution_cipher

https://www.youtube.com/watch?v=BgFJD7oCmDE

https://math.libretexts.org/Bookshelves/Applied_Mathematics/Math_in_Society_(Lippman)/16%3A_Cryptography/16.02%3A_Substitution_Ciphers

https://www.cs.utexas.edu/users/byoung/cs361/lecture40.pdf

https://www.nku.edu/~christensen/section%201%20substitution%20ciphers.pdf

http://pi.math.cornell.edu/~mec/2003-2004/cryptography/polyalpha/polyalpha.html