I learned it in school then again at the hand of David Chaum
He taught me that if I kept the key length long the work hard and the hardware self defeating then a digital signature is absolute proof of presence under and agree set of conditions.
We then spoke of operating systems, payments, smart cards, cryptography: asymmetrical and symmetric. Rooted in PKI and the need to assume a trust less world.
Then there is money. We knew, time ago, we could use electrons to replicate notes and coins on ledgers and within balances.
Electronic Passports, National Identity Cards, and Drivers Licenses will have or have had a digital form.
Now we create Digital Assets.
Valued by a market.
Dreaming of unimaginable wealth or food on the table in the morning.