Pure PHP radius class can be used to authenticate users with a RADIUS network access server according to RFC 2865. It connects to a Radius server given its IP address, and requests access on behalf of a user given his password. Once authenticated, the class may return the attributes of the authorized user. This class works with at least the following RADIUS servers: TekRADIUS and TekRADIUS LT (free RADIUS server under Windows); Authenex Strong Authentication System (ASAS) with two-factor authentication; FreeRADIUS; Microsoft Radius server IAS; Radl; RSA SecurID; WinRadius; and ZyXEL ZyWALL OTP (One-Time Password for Two-Factor Authentication, Authenex ASAS branded by ZyXEL).
libapache2-mod-scramble-ip is an Apache 2 module that works like mod_removeip, but instead of just overwriting the IP address with 127.0.0.1, it encrypts the IP address. This way you always get an IP address to work with (in scripts, etc.) and have the ability to use tools like awstats to analyze your logs. It's in alpha status, but working on some Apache 2 servers, and the 'cost' (load) should be small and reasonable.
Keyczar is a cryptographic toolkit designed to make it easier and safer for developers to use cryptography in their applications. It supports authentication and encryption with both symmetric and asymmetric keys. Cryptography is easy to get wrong. Developers can choose improper cipher modes, use obsolete algorithms, compose primitives in an unsafe manner, or fail to anticipate the need for key rotation. Keyczar abstracts some of these details by choosing safe defaults, automatically tagging outputs with key version information, and providing a simple programming interface.
The Cryptographic Implementations Analysis Toolkit (CIAT) is a compendium of command line and graphical tools whose aim is to help in the detection and analysis of encrypted byte sequences within files (executable and non-executable). It is particularly helpful in the forensic analysis and reverse engineering of malware using cryptographic code and encrypted payloads.
MonoDecrypt uses pattern matching and its knowledge about character frequencies in order to decrypt messages encoded with a monoalphabetic substitution cipher. MonoDecrypt can decrypt texts of any language, as long as it has sufficient information about the language. Depending on the information you give it, the tool decrypts about 50%-100% on its own. Then you can decrypt the remaining data by filling the gaps or correcting bad guesses. MonoDecrypt can also encrypt texts using monoalphabetic substitution.