Christopher has no known social media accounts but he does have a Wikipedia page.
https://en.wikipedia.org/wiki/Christopher_Tarnovsky
Biography
Christopher has some early 2000's videos on youtube from Black Hat and DEFCON and then disappears until about 2019 when some newer video's appeared. His work reverse engineering and working with bare silicon is worth watching for anyone interested in this level of security analysis.
He seems to be most well known for his work with DirecTV and NDS which led to legal troubles. This could be the reason he disappeared from the public for so long. Below is a connection of videos and articles.
Links
How to Reverse-Engineer a Satellite TV Smart Card - This Wired.com video and article is a brief look into Christophers lab and a very high level look at what he does to gain access to the Integrated circuit die.