Announcing digitalwitness.org - free public signing (witnessing) service At present it's in open/public Beta.

At present the ssh interface is open, other(s) (most notably web) will likely follow in time.

Let's say you have a (possibly) large digital artifact (or archive file of such items). Or even possibly much smaller item. Suggested approach is to get secure hash/digest of the item, e.g.: $ sha512sum digital_artifact_file 3ddd987f33a96b50777d15f7850d80d8e30badf12501289d28d5ee4857d62c25c2c700b6a1313cace8b128fe1e4d1ff4787d70c46e1f633e5e4589bf3f2343ba digital_artifact_file $ Then get that hash/digest signed, e.g.: $ ssh -nT digitalwitness@digitalwitness.org -- 3ddd987f33a96b50777d15f7850d80d8e30badf12501289d28d5ee4857d62c25c2c700b6a1313cace8b128fe1e4d1ff4787d70c46e1f633e5e4589bf3f2343ba

$ For more information, help, public signing key, etc., just run without any "command" or arguments thereof, e.g.: $ ssh -nT digitalwitness@digitalwitness.org And that will provide one with much relevant information, and including important details (e.g. the signed data is signed without first adding any implicit newline on the end, though one can explicitly provide that if desired).