/* create a signature of 'index' (0 for author, other values for distributors)
using the private 'key' (filename) and the certificates 'certs' (filenames)
as trusted chain */
/* create a signature of 'index' (0 for author, other values for distributors)
using the private 'key' (filename) and the certificates 'certs' (filenames)
as trusted chain */