Security and Cryptography is a free Android application that serves as a reference book for computer security training and cryptography knowledge, while also providing a set of handy security tools. The app offers several sections covering topics such as CEH lessons, tutorials, flashcards, exam questions with answers and hints, cryptography tutorials, hash generators and an HTTP testing tool. The content is informative and well-organized, making it easy to navigate and understand.

One particularly useful feature of Security and Cryptography is the inclusion of hints and answers for the CEH exam questions, which could be especially helpful for those preparing for the certification. Additionally, the hash generator and HTTP testing tool are valuable resources for security testing and analysis. Overall, Security and Cryptography is a comprehensive application that provides valuable information and tools for anyone interested in computer security and cryptography.