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 It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired. Top of Page Digital signature assurances The following terms and definitions show what assurances are provided by digital signatures. Authenticity The signer is ...

Find out how to submit a request for a refund for a purchase of digital Xbox content.

About digital signatures and certificates in Office, and buying a digital certificate from a certificate authority or create your own.

Contact Microsoft Support. Find solutions to common problems, or get help from a support agent.

To learn about digital signatures (also known as digital ID), what they can be used for, and how to use them in Word, Excel, and PowerPoint, see All about digital signatures. Create a signature line in Word or Excel (desktop) In the document or worksheet, place your pointer where you want to create a signature line. On the Insert tab, select Add a Signature Line in the Text group. In the ...

Learn how to add all your different accounts to the Microsoft Authenticator app.

Many apps allow you to authenticate by entering a code on another device such as a PC. If you want to sign in on a remote computer to install Authenticator, follow these steps.

Learn how to sign in and create app passwords for Microsoft apps and devices that don't support two-step verification.

注意: 此内容可帮助你使用工作或学校帐户。 如果在个人Microsoft帐户上遇到验证码问题，请参阅 验证码问题疑难解答。

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