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Digital Signing of Microsoft 2007 Office System Documents

Microsoft 2007 Office system provides many security improvements over its predecessors, including digital document signing. By digitally signing a document, you can confirm that you are the originator of the document and help prove that the document has not changed since the time you signed it. This white paper introduces the reader to digital signatures: what they are and how to use them.

You can digitally sign a document for many of the same reasons you might place a handwritten signature on a paper document. A digital signature is used to help authenticate the identity of the creator of (authenticate: The process of verifying that people and products are who and what they claim to be. For example, confirming the source and integrity of a software publisherâ€™s code by verifying the digital signature used to sign the code.) digital information â€” such as documents, e-mail messages, and macros â€” by using cryptographic algorithms.

Digital signatures are based on digital certificates. Digital certificates are verifiers of identity issued by a trusted third party, called a certification authority or CA. This works similarly to the use of standard identity documents in the non-electronic world. For example, a trusted third party such as a government entity or employer issues identity documents such as driverâ€™s licenses, passports and employee ID cards on which others rely to verify that a person is whom he/she claims to be.

Digital signatures help to establish the following authentication measures:

Authenticity The digital signature helps to assure that the signer is whom he or she claims to be. This helps prevent others from pretending to be the originator of a particular document (the equivalent of forgery on a printed document).
Integrity The digital signature helps to assure that the content has not been changed or tampered with since it was digitally signed. This helps prevent documents from being intercepted and changed without knowledge of the originator of the document.
Non-repudiation The digital signature helps to prove to all parties the origin of the signed content. “Repudiation” refers to the act of a signer’s denying any association with the signed content. This helps prove that the originator of the document is the true originator and not someone else, regardless of the claims of the signer. A signer cannot repudiate the signature on that document without repudiating his or her digital key, and thus other documents signed with that key.

Read more and download the withe paper here