You can't guarantee a trusted project by just meeting them the first time; trust is being built gradually, unless for already existing projects that have built a reputation over time, but for security concerns, anyone seeking jobs from such companies should be mindful of the type of information they give out, and on the line of private key, it's called a private key for a reason, which means it shouldn't be shared, and any employer that asks for such is already a sign of a scam.