Encrypted server name indication (ESNI) is a way to plug a privacy-hole that remains in the Transport Layer Security (TLS) protocol that’s used as the security layer for the web. OpenSSL is a widely used library that provides an implementation of the TLS protocol. The DEfO project is developing an implmentation of ESNI for OpenSSL, and an ESNI-enabled web server as a demonstration and for interoperability testing. Over time, DEfO will demonstrate integration of ESNI with other tools that use TLS.
Our OpenSSL fork supporting ESNI is on github.