RSA Shirt

Three lines of Perl that implement RSA encryption, written by Adam Back in 1995. At the time, the U.S. government classified strong cryptography as a munition under the International Traffic in Arms Regulations — exporting it was a federal crime carrying up to 10 years in prison. Cypherpunks printed these three lines on T-shirts and wore them to airports as deliberate civil disobedience. The shirts were, technically, illegal weapons.The protests helped force the late-1990s loosening of cryptographic export controls and contributed to the legal precedent — established in Bernstein v. United States (1999) — that source code is protected speech under the First Amendment.

Source: Code by Adam Back, 1995. Originally published at cypherspace.org during the cypherpunk export protests. Attribution given as a matter of historical record; permission inquiry pending.