Improve your Spanish while learning cryptography

Manuel Lucena is a professor from Jaen University who has a great book on cryptographic algorithms and who is kind enough to provide us a free PDF version.

There is only a catch on this offer: it's only available in Spanish. What a good opportunity for practicing your newly acquired skills!!

Contrary to what happened in the classroom, the book provides a detailed view of many cryptographic algorithms, including DES, IDEA, AES, RSA, ElGamal, DSA, ... etc

Update: For those of you that still prefer a book written in English you can download this one. Though a bit aged it is still a very solid book.