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 It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.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

了解如何关闭双重验证。 双重验证是一项可选的安全功能，通过使用两种形式的身份，即密码和联系方式（也称为安全信息），这样别人更难进入您的 Microsoft 帐户。

A popular tactic of criminals is the "fake order" scam. The way it works is that you get a message, usually in email or text, that appears to be a routine confirmation for an order. Of course, you never ordered whatever product or service it's confirming. The message looks common enough, and it says that money will be charged to your credit card or withdrawn from your bank account for the ...

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

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Want to add a padlock to your email messages? You can use encryption and digital signatures in new Outlook, classic Outlook, and Outlook on the web for work or school accounts to increase the security of messages. Encrypting an email message in Outlook means it's converted from readable plain text into scrambled cipher text. Only the recipient who has the private key that matches the public ...

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

Notes: Security info doesn't support using phone extensions. Even if you add the proper format, +1 4255551234X12345, the extensions are removed before the call is placed. If you don't see a phone option, it's possible that your organization doesn't allow you to use this option for verification. In this case, you'll need to choose another method or contact your organization's help desk for more ...

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

Learn how to protect your PC, identity, and data from tech support scams.