During one of my many surf sessions on the web, I found the eBook ‘Security Engineering’ from Bruce Schneier.
You can download the PDF-files per chapter at:
My goal in making the book freely available is twofold. First, I want to reach the widest possible audience, especially among poor students. Second, I am a pragmatic libertarian on free culture and free software issues; I think that many publishers (especially of music and software) are too defensive of copyright. I don’t expect to lose money by making this book available for free: more people will read it, and those of you who find it useful will hopefully buy a copy. After all, a proper book is half the size and weight of 300-odd sheets of laser-printed paper in a ring binder. (My colleague David MacKay found that putting his book on coding theory online actually helped its sales. Book publishers are getting the message faster than the music or software folks.)