OpenSSL is a framework which implements the secure socket layer. It ships with a program/library which gives you access to all those functions.

CSR.plus is described as 'Free SSL/TLS toolkit that runs in your browser. Generate RSA or ECDSA key pairs and certificate signing requests (CSR), decode certificates and CSRs, check SSL deployments, and monitor certificate expiry' and is an website. There are 1 alternatives to CSR.plus, not only websites but also apps for Mac, Windows, Linux, BSD and Haiku. The best CSR.plus alternative is OpenSSL, which is both free and Open Source.
OpenSSL is a framework which implements the secure socket layer. It ships with a program/library which gives you access to all those functions.
