3.2.19 Is RSA patented?

  RSA is patented under U.S. Patent 4,405,829, issued 9/20/83 and held by Public Key Partners (PKP), of Sunnyvale, California; the patent expires 17 years after issue, in 2000. RSA is usually licensed together with other public-key cryptography patents (see Question 3.1.5). PKP has a standard, royalty-based licensing policy which can be modified for special circumstances. If a software vendor, having licensed the public-key patents, incorporates RSA into a commercial product, then anyone who purchases the end product has the legal right to use RSA within the context of that software. The U.S. government can use RSA without a license because it was invented at MIT with partial government funding. RSA is not patented outside North America.

In North America, a license is needed to ``make, use or sell'' RSA. However, PKP usually allows free non-commercial use of RSA, with written permission, for personal, academic or intellectual reasons. Furthermore, RSA Laboratories has made available (in the U.S. and Canada) at no charge a collection of cryptographic routines in source code, including the RSA algorithm; it can be used, improved and redistributed non-commercially (see Question 3.8.10).