I'm using .Net to build a commercial application, i.e. a secure chat application. This application is using RSA and Rijndael algorithms.
Do we need licenses for using RSA and Rijndael algorithms for commercial product?
No, you don't need any licenses for neither of them.
Patents for RSA have expired on September 21, 2000. Even before that, it was also released as public domain.
Rijndael was submitted to NIST as Federal Information Processing Standard for AES, and is officially declared by authors to be patent free.
For RSA algorithm, no license required for any products developed after September 6, 2000. The date is important.