On the platform for which we have made our implementation, entering information is time consuming. The graphical user interface is pen-based, and writing is rather slow. Some fairly long strings (such as file names with an associated path) have to be entered to uniquely identify a file, or selected from a list of frequently used strings.
On the PDA, to create a digital signature on a certificate takes about 5 seconds while verifying a signature takes about 10-15 seconds. While the process of signing certificates is mandatory, verifying the signature on the PDA is not. The receiver may choose to pass the certificate on to FR without verifying that it is correct. FR runs on Unix, and verification of a signature in this environment takes fractions of a second and does not pose a performance problem in the intended target environment.