A method for transmitting a data signal by a transmission unit of a wireless multiple-inputmultiple-output communication system. Such solutions and methods find particular application in the fabrication of a dual damascene structure following removal of excess portions of a silver-containing metal layer from a device surface. An operator accesses the electronic message and the linked DTF image to resolve the check adjustment case. Several dissimilar digital signature algorithms may be used to reduce vulnerability from algorithm compromise, and subsets of multiple digital signatures may be used to reduce the scope of any specific compromise.