Public/Private key pairs, verifying messages and images are from someone you know in your local community or that you trust through your relationship with someone else
I also think that AI is just a wake up call - photoshop and other digital manipulation tools have already made so much stuff on the internet fake. AI just makes it more accessible to everybody
I’m sure if I redownloaded instagram I’d find that 20% of images in my feed are doctored in some way, and “photoshop” has been used in propaganda since before Stalin