List of useful tools and web pages

CrypTool 2 (CT2) is the successor of CrypTool 1, the most wide-spread free and open-source e-learning tool for cryptography and cryptanalysis. It has more than 200 cryptologic functions ranging from classic (like Caesar, Enigma) to modern (like AES, RSA, homomorphic encryption) crypto. It uses the concept of visual programming to present cryptographic processes; and it focuses on offering the according cryptanalysis methods too.
See this site for CrypTool 2, and this site for the whole CrypTool project.

Klausis Krypto Kolumne is a blog about historical cryptology. It covers unsolved encrypted messages from the last 500 years, vintage encryption machines, codebreaking, hidden messages, and similar topics. The blog started in 2013; meanwhile Klaus has published almost 1,000 posts. The readers of this blog have proven extremely successful in deciphering encrypted messages, with numerous encrypted postcards, letters, diaries, notes, and inscriptions having been solved over the years.
For more information visit the blog .

DECODE involves the collection of ciphertexts and keys from Early Modern times, the systematic automatic detection of various cipher types, the development of algorithms for (semi-)automatic decryption of different types of ciphers, and the creation of language models and pattern dictionaries for early variants of fifteen European languages: Czech, Dutch, English, Finnish, French, German, Hungarian, Icelandic, Italian, Latin, Polish, Portuguese, Russian, Spanish, and Swedish.
See this site for the DECODE project.

Crypto Cellar is a site dedicated to cryptology and cryptologic history with special focus on cipher machines and the cryptanalysis of these machines and other more complex cryptologic systems.
See this site for the Crypto Cellar project, and this site for the Crypto Cellar Tales blog.

Cryptiana: Various codes and ciphers used through history are described.
See this site for more details.

Cryptobooks is an online bibliography of books about or dealing with cryptology from the 15th century until now. Its database contains more than 500 listed books and more than 350 listed authors.