Applied Cryptography
Bruce Schneier's 1994 book that handed a generation of programmers both the protocols and the source code, right in the middle of the crypto wars.
The first edition appeared in 1994, the second in 1996. It collected nearly everything known, from Diffie-Hellman and RSA to Schneier's own Blowfish, with C code in the appendix. That made it a political object: the US State Department cleared the printed book for export but refused the floppy disk containing the same code that Phil Karn wanted to ship. The absurdity that paper was speech while bits were munitions became one of the sharpest arguments of the crypto wars.
Schneier later qualified the book's message himself. In Secrets and Lies (2000) he wrote that mathematics isn't enough, and the follow-up Practical Cryptography, with Niels Ferguson, was about everything around the maths that actually breaks.