Make signature timestamps trustworthy

[satazor]

Description

Ideally, a signature time stamp would be trustworthy. Here’s a few ideas:

• The relying party asking for a signature defines a timestamp. If the person signs it, it means that he attests that the timestamp is correct
• Use a blockchain anchor, such as a block, so that both parties can verify the block timestamp
• Use a timestamp attester service

We need to brainstorm this subject and commit to a solution.

Acceptance Criteria

• [ ] TODO