Many books on Web security and cryptography are available. We recommend the following books:
Web Security, L. Stein (Addison Wesley). An excellent, comprehensive book with both technical and nontechnical depth.
Applied Cryptography: Protocols, Algorithms, and Source Code in C, B. Schneier (John Wiley and Sons). Covers the field of cryptography in technical depth.
The Code Book, S. Singh (Anchor Books). An enjoyable popular science book.
Building Secure Servers with Linux, M. Bauer (O'Reilly).
Security Engineering, R.J. Anderson (Wiley). An excellent all-round book.
Web security, privacy and Commerce, S. Garfinkel, (O'Reilly).
The RSA encryption web site, http://www.rsa.com.