An example operation may include one or more of receiving, by a document server, a hash of data generated by an author registered with a blockchain, sending, by the document server, the hash of the data to a timestamp authority (TSA) to be time stamped, receiving, by the document server, a timestamp reflecting when the hash of the data was received by the TSA and forwarding the timestamp to the author, receiving a combination of the hash of the data and the timestamp (time/hash) signed by the author and forwarding the time/hash to the blockchain, receiving, by the document server, the time/hash signed by the TSA, and forwarding the time/hash signed by the TSA to the blockchain.