What technologies do you think exist but are kept away from public disclosure?

probably lots of backdoors and decryption tech, but not much else.

• More modern nukes. Considering the most modern nuke (b83) was invented at late 1970s, and officially put in service at 1983. It's very likely a new nuke was invented in secret.
• Bio weapons more lethal than botulism
• Cyber attack bots
• Other warfare related stuff

Space tech.

because imo the major event of the 22th century is probably gonna be space travel/warfare/colonialization

and any nation would be dumb to not keep their space stuff well-hidden lest someone steals/copies it

also probably growing artificial human organs and/or research on human gene editing