Digital signatures and certificates – Microsoft Support

For more information, see Add or remove a digital signature in Office files .

More and more people and organizations are using digital documents instead of paper documents to conduct day-to-day transactions. By reducing dependency on paper documents, we are protecting the environment and saving the planet’s resources. Digital signatures support this change by providing assurances about the validity and authenticity of a digital document.

The following is an example of a signature line.

A digital signature is an electronic, encrypted, stamp of authentication on digital information such as email messages, macros, or electronic documents. A signature confirms that the information originated from the signer and has not been altered.

Signing certificate and certificate authority

Signing certificate     To create a digital signature, you need a signing certificate, which proves identity. When you send a digitally-signed macro or document, you also send your certificate and public key. Certificates are issued by a certification authority, and like a driver’s license, can be revoked. A certificate is usually valid for a year, after which, the signer must renew, or get a new, signing certificate to establish identity.

Note: You can learn more about public and private keys in this article.

Certificate authority (CA)     A certificate authority is an entity similar to a notary public. It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.

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