Having some time between Christmas eve 2023 and the New year day,
I had a close look into * David Wong *s book ** Real-World Cryptography **[1].
Since 20 years I teach IT Security at Universities and since about
10 years I've used a certain 'picture' to illustrate cryptograhy, which I use
in particular in my book 'Technik der IP-Netze' [2].

Apart that, I implement cryptographic routines into my own developments, you can find here [3]. To my surprise, the ideas and the outline of David's book is very close to my own descriptions, making me believe I was not that wrong.

David introduces cryptographic primitives as I do; though in a different order and provides a particular sceptical view on current implementations (except of those generated by Daniel J. Bernstein).

For most people, still Bruce Schneier's ** Applied Cryptography ** (1996) is one
of the standard works; rather I really would consider David's current book to fill a
gap existing now for almost 30 years.

Two thoughts I like to share: RSA is difficult since you don't now the group
to reverse the public key (and *not* generating n = p*q or phi=(p-1)*(q-1)).
Calculating the inverse (d, the private key) of the RSA's public key is *easy*
once you have phi and e: d = (1+phi)/e; unlike mentioned here and in most other
text books about RSA.

[1] www.manning.com/books/real-world-cryptography

[2] www.fehcom.de/pub/tipn.html

[3] www.fehcom.de/ipnet/djbware.html