A mechanism for calculating your trust of an individual

This is an idea that's been on my mind for a couple of years. Something reminiscent of PageRank, but for individuals, as in propagating trust. I trust B, and B trusts C, and as such, C is trustworthy to some extent. There are several aspects of trust, I guess. Like accountability, correctness of memory, moral character (could be deterred by some forms of law violations?) ... dunno if that is relevant, though. Maybe only the intuitive meaning of "trust" is enough. There is no universal trust, all goes back to you trusting "seed individuals", that in turn trust other people. Maybe a scale of 0-11 will determine your trust of an individual, so that you can get "circles" of trusted individuals. Maybe you need negative trust, or maybe that is what 0 is for, effectively shutting down that individual in your trust graph. But, other individuals may not trust the one who is zero-ing that individual, and may trust him. If implemented as an app, to verify that you are a trusted individual in whatever context (maybe when starting a company), you bring up your app, and it shows a QR-code. You scan it with your app and your trust of that individual is calculated. Maybe this whole concept is defeated by counterfeiting? Just screenshotting that QR-code makes you copy that individual ... But then again, copying someones ID is just as problematic. Any thoughts?