python-nss is a Python binding for NSS (Network Security Services)
and NSPR (Netscape Portable Runtime). NSS provides cryptography
services supporting SSL, TLS, PKI, PKIX, X509, PKCS*, etc. NSS is
an alternative to OpenSSL and used extensively by major software
projects. NSS is FIPS-140 certified.

NSS is built upon NSPR because NSPR provides an abstraction of
common operating system services, particularly in the areas of
networking and process management. Python also provides an abstraction
of common operating system services but because NSS and NSPR are
tightly bound, python-nss exposes elements of NSPR.