I remembered it correctly: It's the RSA part of OpenSSL which was cracked (or leaked to be exact), 11 years ago (wow, time flies).

Summary is here [0], and paper is here [1].

[0]: https://www.theregister.com/2010/03/04/severe_openssl_vulner...

[1]: http://web.eecs.umich.edu/~valeria/research/publications/DAT...