What is Computer Science: An Information Security Perspective
The material is available under a Creative Commons Attribution-ShareAlike license:
You can get it as as one (fairly large) book, or individual chapters:
- Part I : Foundations
- Part II : Cryptography
- Part III : Security
- Part IV : Advanced
A printed version of this material (i.e., the 1st edition) was published by Springer, all royalties from which are donated to the UK-based Computing At School (CAS) group.