Is RSA Patented?

RSA is patented under U.S. Patent 4,405,829, issued September 20, 1983 and held by RSA Data Security, Inc. of Redwood City, California; the patent expires 17 years after issue, in 2000. RSA Data Security has a standard, royalty-based licensing policy which can be modified for special circumstances. The U.S. government can use RSA without a license because it was invented at MIT with partial government funding.

In the U.S., a license is needed to "make, use or sell" RSA. However, RSA Data Security usually allows free non-commercial use of RSA, with written permission, for academic or university research purposes. 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 174).