cryptography

He began studying cryptography, code-breaking and puzzle-solving books.

Cryptography is the art of coding and decoding information between parties.

They are much more difficult to decipher than was the cryptography left by the pirate Kidd.

He held up a heavy volume called Cryptography for the Student.

In cryptography it's a number, or letter, thrown in for the sake of appearance, or to confuse.

He is the author of a work on cryptography, I believe, though I am ashamed to say I haven't yet read it.

I am not altogether ignorant of cryptography; it was Trevisa's favorite pursuit when we were at college.