What are EXE Digital Signatures?

And what is installation error 10091?

WHAT TO DO: Because the digital signature check (see below for full details) is failing, you know that the downloaded EXE has been modified in some way during the download process (or as it was saved to your hard drive). We recommend taking the following actions:

Run anti-virus software: Many viruses work by modifying an EXE as they are saved to your PC. This may have happened on your PC. Run anti-virus software on your PC first, to verify that your PC is virus-free. Then download a new install EXE and try again.

Change how you download the EXE: What download program are you using to download the EXE? We have actually seen a couple of cases where the download manager program had a bug and caused the downloaded EXE to be changed in some way. Switch to another download program, such as Internet Explorer, or the FTP program included with your computer.

Contact us: If problems persist, please Contact Us.

Visualware Installation EXE's are digitally signed: A feature of the installation program that Visualware uses to produce installation EXE's is that every EXE is digitally signed to detect tampering. The following illustration demonstrates this signing process:

Validating the digital signature: When you run an installation EXE downloaded from our download server, the digital signature of the EXE is calculated and compared to the signature stored in the EXE. If the EXE has changed in any way (like changing a '1' to a '6' in the example below), the digital signature will not match and an error #10091 will be reported. The following illustration demonstrates this validation process:

So, if you are getting a digital signature error, the EXE you are running is not identical to the EXE on our download server. The EXE has been modified in some way! If it did match byte for byte, the digital signature will (and must) match.

Notes: In these illustrations, simple addition is used to illustrate how a digital signature is calculated. The actual digital signature process is a much more complicated mathematical algorithm.