What is PKI? And how it secures just about everything online – Digitaleclub
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What is PKI? And how it secures just about everything online

PKI definition

Public key infrastructure (PKI) is a catch-all term for everything used to establish and manage public key encryption, one of the most common forms of internet encryption. It is baked into every web browser in use today to secure traffic across the public internet, but organizations can also deploy it to secure their internal communications and access to connected devices.

The most crucial concept involved in PKI is, as its name implies, the public cryptographic keys that are at its core. These keys not only are part of the encryption process, but they help authenticate the identity of the communicating parties or devices. 

Why is PKI important? It’s because this combination of encryption and authentication makes trustworthy online communication possible.

How does PKI work?

The most important concepts to understand to grasp how PKI works are keys and certificates. A key, as already noted, is a long string of bits — a number, in other words — that’s used to encrypt data. For instance, if you used the ancient and simple Caesar cipher with a cryptographic key of 3, that would mean that every letter in your message is replaced by one three letters later in the alphabet — A becomes D, B becomes E, and so forth. To decode its message, your recipient would need know not only that you were using the Caesar cipher but that your key was 3.

Obviously the mathematics behind modern encryption is much more complicated than this. One of the ways it’s different gets around a somewhat obvious problem with the Caesar cipher: you have to somehow let your recipient know the key used to encode the encrypted message. PKI gets its name because each participant in a secured communications channel has two keys. There’s a public key, which you can tell to anyone who asks and is used to encode a message sent to you, and a private key, which you keep secret and use to decrypt the message when you receive it. The two keys are related by a complex mathematical formula that would be difficult to derive from brute force. If you want to get into the weeds on this form of encryption, known as asymmetrical cryptography, HowStuffWorks has a good deep dive.

So that covers how data is encrypted within a public key infrastructure. But remember, PKI is widely used because, in addition to encrypting messages, it also lets you know that the person with whom you’re exchanging encrypted messages is who they say they are. That’s where certificates come in.

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