Stephan Neuhaus <neuh...@st.cs.uni-sb.de> writes: > On Oct 1, 2009, at 16:46, Perry E. Metzger wrote: >> It is also completely impossible to prove you've deleted a >> record. Someone who can read the record can always make a copy of >> it. Cryptography can't fix the DRM problem. > > Sorry, I should have clarified that. We don't want to verify that Bob > has in fact deleted the patient record, we just want to verify whether > Bob *claims* to have deleted the patient record *within the time span > given*. If Alice later finds out that Bob has lied, she will have this > signed claim, with which she can take him to court.
If you have that more limited need, the Haber & Stornetta protocol will likely do what you want, provided you can set something up to publish the "widely witnessed events". (They had a company for a while to do timestamping that published the hashes in the New York Times classifieds. I think when they wrote their paper, the idea that newspapers might soon cease to exist was not anticipated -- a more modern system will need some sort of more durable model.) Perry -- Perry E. Metzger pe...@piermont.com --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to majord...@metzdowd.com