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 It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.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 ...

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The Microsoft Authenticator app helps you sign into your accounts when you're using two-step verification.

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This article answers common questions about Microsoft Authenticator. Select the headings below to see more information.