What is a Public Key Certificate?

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  • Written By: Dorian Hunter
  • Edited By: Angela B.
  • Last Modified Date: 11 March 2020
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A public key certificate is a cryptographic document utilized by computers to verify the identity of a named party when communicating over the Internet or other network. These certificates typically consist of a digital signature of a certifying authority, a sender’s public key, and other identifying information to verify a sender’s identity to a recipient. Public key certificates are an established part of secured network and Internet communications.

A public key certificate falls within the realm of computerized cryptography, which involves the conversion of data into a secure format that renders it unreadable to others without the proper means of rendering it decipherable. A vital component of a public key certificate is the public key algorithm, a kind of mathematical code. The public key algorithm enables encryption of data exchanged between computers while providing for secure remote access to a user through interaction with a private key. Public key certificates' encrypted format helps to provide privacy in communications, especially in sensitive e-mail correspondence and electronic commerce.


Public key certificates consist of multiple components, such as textual and numerical naming of the recipient of the document, the recipient’s digital signature, and the certificate authority that rendered the public key. Important data like the date issued and expiration of the certificate, the encryption algorithm and an identifying code to show the authenticity of the certificate is included. Certificates are issued for a limited time period, must be renewed once or several times a year, and can be revoked if circumstances warrant.

A certification authority is responsible for issuing public key certificates, and can be private, commercial, or governmental in nature. Private and commercial authorities typically charge for the issuance of digital certifications, which are accepted by most Internet-based web-browsing applications. These entities take steps to protect against the manipulation of certificates and help to maintain the confidentiality of sensitive data held within the certificate. Although it is ultimately up to the user visiting a website to determine communications safety, certification authorities are obliged and trusted to verify the identity of those to whom they issue public key certificates.

The most common use of a public key certificate is for interaction with Internet-based websites. A recipient’s computer validates a sender’s website credentials, so the user has authentic interaction with the subject website and a level of security. This type of certificate–based authentication plays an important part in secure communications and electronic commerce.


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Post 3

@nony - I am not an expert but I think it’s an encryption method. They take your private key and use it to create what’s known as a “hash” of whatever it is you’re transmitting over the Internet.

The hash looks garbled to anyone who doesn’t have your key. They append the hash to your document and I think that’s what is called the digital signature.

That’s as much as I understand anyway. Since it’s based on your key and your document, it’s as much a signature as your handwritten signature would be. In other words, it’s unique to you.

Post 2

@miriam98 - I get the part about the security certificate. However, I’ve never understood the concept of a digital signature. The phrase always seemed counterintuitive to me. How can you digitally sign something?

Post 1

As a matter of practice, I wouldn’t engage in ecommerce with any website that didn’t provide some sort of security certificate. The way you’ll know is that the website will usually give you some sort of message to that effect, or conversely, if there is no valid certificate the web browser will let you know that as well.

You don’t need to go overboard and avoid any website that doesn’t have a certificate – only those which engage in ecommerce. For run of the mill Internet browsing it doesn’t matter too much, because you are not exchanging confidential information like credit card numbers.

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