Is there a server that can help in the following scenario:
- Alice (a client) generates some data (a hash of something)
- Alice sends the data to the server in question
- the server appends Alice's data with the current time stamp (i.e. UTC)
- the server signs the resultant object with the server's private key
- the server sends/responds to Alice with the signed object
As a result, Alice now can prove to Bob (or anyone else) that she had the hash at the time of the time stamp. Note: the server's public key is publicly available.