+The current algorithm is dumb, that is it does not use any hashing of
+the file content. I tried md5 on the whole file, which is not
+satisfactory because files are often never read entirely hence the md5
+can not be properly computed. I also tried XOR of the first 4, 16 and
+256 bytes with rejection as soon as one does not match. Did not help
+either.
+