[foo92691]

Applied Cryptography is an excellent book, but it is very very old. Nearly 25 years old.

The foreword of the semi-recent (2015) "20th anniversary edition" (which appears to be a reissue of the 2nd edition) even recommends that you look for a more modern reference.

And one of the lessons of the last decades is that programmers should generally not be implementing their own cryptography unless that is their specialty.