Annotations which verify their content

context: OAC (and SharedCanvas and IIIF) in web applications for manuscript
studies using linked open data structures.

*Image checksum or signature:*

In IIIF it is possible that the underlying image being served has changed
since last annotated, but the URI used to request it has not changed. If
offered and consumed the upon the first link up, I would love to store some
checksum or signature to verify the same image is used when delivered
later. While this may be resolvable by also requesting some sort of image
version header, a checksum would also allow me to (possibly) discover if
the same image which used to be available at one location is indeed the
same as another available image (assuming something like md5 or other
collision-resistant checksum).

I have not worked with crypto or verification before, but it would be nice
to use a checksum like a UUID in cases that the URI does not do that. As I
understand it, this would also be possible with other media, with varying
degrees of error.

Would such a thing be a request header? metadata? a verification
annotation? Has anyone done this? If I generate my own and store it is that
good enough?

Patrick Cuba
Center for Digital Humanities
Saint Louis University