ecdsa – What previously existing technologies made Bitcoin possible?

When watching a tutorial, they mentioned that Bitcoin is based off 4 or 5 technologies that existed for at least a decade before Bitcoin. Satoshi Nakamoto was the first person to combine them all into a digital currency.

I’m aware of at least some of them – SHA-256, ECDSA, peer-to-peer distributed ledger – but want to try and understand all of them.

What other technologies underpin Bitcoin?