On Nov 4, 2011, at 2:09 AM, Chris Morris wrote: > One argument for archiving images has been that reprocessing could > demonstrate deliberately deceptive structures. > > In fact, what is needed for this is not necessarily the image. It is the last > data file that was produced by a trusted computer.
Although this is a good idea from the perspective of storage, it is difficult to implement. For this idea to work, you need a (1) certificate system, (2) certificate authority. The certification is necessary to verify that the data file was indeed generated by a trusted computer. The chosen file needs to be certified by the authority and the certification archived on a trusted system. None of these requirements are terribly problematic. The infrastructure for a certificate system is free in the form of openSSL. Almost any lab or institution could easily become a certificate authority. The storage requirements for the certificates are trivial. For example, if a certificate were 2 KB, then, for the 8,000 structures per year, the storage requirements would be 1.6 MB. After 1000 years, we would fill up my $14.95 2 GB thumb drive. The difficulty is that certification should be done on the file before it is transferred from the trusted computer. This requires inserting the certification process somewhere in the transfer pipeline, which is difficult because it requires all the synchrotrons to actually implement it. Allowing the user to produce the certificate after transfer is as useful as having no certificate system at all. Then there is the issue of data collection on a home source. James
