Cryptography textbook Might come as a rather strange request but does anyone know a textbook on cryptography that is small and short, say around 300 pages max. I am tired of having a sore shoulder from carrying 5 heavy math textbooks. Want to carry around a cryptography textbook for anytime reading that is concise but I won't be picky. Just need something light.  

I'll leave the weigh-in to you. But you may be interested in this selected text and course page by an outstanding teacher - Ken Ribet
http://math.berkeley.edu/~ribet/116/
The text is by three also outstanding teachers:
http://www.amazon.com/Introduction-Mathematical-Cryptography-Undergraduate-Mathematics/dp/0387779930/ref=sr_1_1?ie=UTF8&s=books&qid=1219201611&sr=8-1
