Microsoft Office 2007 provides many improvements in security in comparison with its predecessors. And one of new functions is possibility of digital signature of documents. Signing a document, you confirm that you are the creator of document, and it will prove that a document wasn't changed since you created its creation.
You can create a digital signature for a document because of the same amount of reasons, on which you can affix your signature to a paper document. A digital signature is used for identification of digital documents creator (such as ordinary document, e-mail and macros) by 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 driver’s licenses, passports and employee ID cards on which others rely to verify that a person is whom he/she claims to be.
Digital certificates can be issued by certification authorities within an organization, such as a Windows® Server 2003 server running Windows Certificate Services, or a public certification authority such as VeriSign or Thawte.
