Bouncy Castle jar files are used for encryption purposes. Peoplesoft also uses the jar files delivered by Bouncy Castle. It is installed in Webserver directory of PS_HOME. Below is the exact location for the file.
and the file name will start with bcprov eg. bcprov-jdk13-128.
Exact file name may be different depending on the jdk installed. For latest releases and update on Bouncy Castle please visit http://www.bouncycastle.org/latest_releases.html.