Countersigning needed for digital signatures to go big

In fact, you should have a pre-defined list of public keys that needs to be used and countersign your signature for your signature to be valid

A big problem with digital signatures (sometimes called electronic signatures) is that somebody can steal the signature making device and sign away on stuff, pretending to be you.

One way of mitigating that is to have your signature only to be valid if other people countersign it. For any contract that isn't just a small purchase, it is worth the extra effort to call up some people who trust you and ask them to countersign, or meet up in person and do that. Wikipedia - Countersign (legal).

In fact, you should have a pre-defined list of public keys that needs to be used and countersign your signature for your signature to be valid. At least m of n of them must be used, and if one of them gets stolen then as long as the original owner still has access to it, there would be enough redundancy that it does not matter as much (but that key should be marked as stolen of course and there should be a threshold for how many such keys can be used).