Digitally signing a model or file can be used to indicate approval of the design. Another user can then detect the signature, verify the signer’s identity, and verify that the design has not been changed since it was signed. Model-specific signatures are displayed graphically in the context of the design. Multiple signatures can be affixed to a single file or model. Hierarchical signing is also supported so that one signature is dependent upon prior signatures. A signature can cover the content of a model or file and all of its references including DGN and DWG references.
Starting with the 2004 Edition, OpenUtilities Substation
saves not only the signer information but also who issued the signer's certificate. In earlier versions, if the user's computer and the signer's computer were not set up to recognize the same intermediate certificate authority (CAs), valid signatures could be viewed as not trusted. By saving the entire chain of certificates leading from the signer back to the trusted root, adequate information is available for any computer to verify a signature regardless of the intermediate CAs it recognizes.
Signatures created in the 2004 Edition and later will not be backward compatible with OpenUtilities Substation
V8.1 because it is possible that the signatures could be larger than the earlier version allows. These signatures will be marked as unverified because they contain information that is not recognizable. Users who want to exchange signatures should all be running the 2004 Edition.
Among other key features, signers can use cells to represent signatures with arbitrary graphics; an API is defined to allow applications to customize where signatures can be placed and how a signer’s identity is authenticated; and there are several ways users can detect valid signatures to prevent spoofing.