Peter Gutmann wrote:
If you're going to produce signed receipts as proof-of-delivery, you're well into S/MIME / PGP territory. This seems to be going way beyond what SSH should be doing (depending on how far you want to take this you'd need to reinvent significant chunks of PGP or S/MIME), it'd be better to just define a signed content type for one of those formats and use that.
I agree that the spec for the signature itself belongs elsewhere - but I can see an argument for building the ability to ask the server to produce such a signature into SFTP. The signature standard need only be incorporated by reference.
As I read it, Jason's only requirement is for the server to sign to say "file X (hash Y) was on this server at time T". This could use signature schemes already in existence, providing that SFTP were able to ask the server to produce the signature and transfer the produced signature back to the client.
-- Jon Bright Silicon Circus Ltd. http://www.siliconcircus.com