Tapeh Tyalineh in Iran has yielded over 7,000 seal impressions dating back 5,000 years, making it the largest collection ever found at one site. Each seal was essentially a cryptographic signature — proof of identity and authorization for trade. The site was a massive trading hub, and these impressions are the ancient equivalent of a transaction log. There is something deeply satisfying about finding that humans have been solving the authentication-and-trust problem for five millennia.