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

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 It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.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

Summary A BitLocker recovery key is needed when BitLocker can’t automatically unlock an encrypted drive in Windows. This is a 48‑digit number that lets you regain access to your drive.

Applies to: Windows 10 Enterprise LTSC 2021 This security update includes fixes and quality improvements that are part of the following update: October 14, 2025—KB5066586 (OS Build 17763.7919) The following is a summary of the issues that this update addresses when you install this update. The bold text within the brackets indicates the item or area of the change we are documenting. [App ...

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Delta Ring (2602.260310-1610) Hey Xbox Insiders! We are releasing a new Xbox Update Preview to the Delta ring today. Continue reading below to learn all about what's included with this update.

What is Secure Boot? Secure Boot is a security feature in Unified Extensible Firmware Interface (UEFI) based firmware that helps ensure that only trusted software runs during a device's boot (start) sequence. It works by verifying the digital signature of pre-boot software against a set of trusted digital certificates (also known as certificate authority or CA) stored in the device's firmware ...

Signing your email messages with a digital ID helps to prove your identity and prevent message tampering.

Download Microsoft Authenticator Microsoft Authenticator is a mobile app that helps you sign in to all your accounts without using a password.