In 19 76 whit was noodling on these problems, and he had a break through. He realized that if we both have safes and we both have our own protected personal keys, we can trust that we're talking to each other without ever having to meet in person. This also solves the second problem of identity, because you know that that's my safe and my mail slod. It was a stunningly elegant idea, something they called public key cryptography.