Digital Fortress by Dan Brown

An influential government intelligence agency, called the National Security Agency's have built an invincible code-breaking machine named TRANSLTR. Led by the deputy director of operation, Commander Trevor J.Strathmore , the intelligence agency built this ultra fast computer which could decrypt sixty-four-character key in less than ten minutes. Codes intercepted by the NSA entered the TRANSLTR as illegible codes and were decrypted in perfectly readable cleartext. All this was an amazing victory for the NSA until the blow hit.

Ensei Tankado, a prior cryptographer who worked in the NSA , a briliant code-writer finally anounced that he had written a brute-force-resistant algorithm, which was unbreakable and would make the giant $2 billion fiasco TRANSLTR obsolete. Discovering this big problem the Commander calls in Susan Fletcher , head cryptographer and a brilliant mathematician, who uncovers a road of crime, leading far than anyone can imagine. She is shocked by the fact that the heart of NSA is about to be crippled not by bombs, or guns but by an unbreakable complex, code.

Betrayed by her confidante, and her supporter, unsure of the people around her, trusting on instincts she fights the cryptography battle, putting her own life, and the life of her love at stake.

In short it is a most thrilling plot, which is bound to keep your nerves tingling till the end. I enjoyed it thoroughly.