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Whenever I try to understand anything about SSL I always have a hard time keeping track of what "key" and "certificate" refer to. I fear many people use them incorrectly or interchangeably. Is there a standard difference between a key and a certificate?

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Certs used for SSL is heavily based on PKI en.wikipedia.org/wiki/Public-key_cryptography –  Zoredache Jul 15 '13 at 18:39

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up vote 12 down vote accepted

A certificate contains a public key.

The certificate, in addition to the public key, contains additional information, such as issuer, what it's supposed to be used for, and any other type of metadata.

Typically a certificate is itself signed with a private key, that verifies its authenticity.

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A certificate haa the public component of a key, not the entire key. –  Zoredache Jul 15 '13 at 18:29
I made corrections. :) –  ultrasawblade Jul 15 '13 at 18:36
@Zoredache If a certificate typically only has a public key, is there a good name to call .p12 or .pfx files that contain certificates and private keys together? –  drs Jul 15 '13 at 18:54
A pkcs12 is an archive format. It may contain a key, or maybe not. I usally try to always be specific when refering about what a particular file contains, or just say pkcs12 file. –  Zoredache Jul 15 '13 at 19:08

An SSL certificate is obtained from a trusted Certification Authority, which vouches for secure connection of the website . SSL certificates usually contain the logo of authentication and also the public keys necessary to encrypt and decrypt data that is to be sent to the computer. SSL Keys Functions

Several SSL keys can be generated during a session. They are used to encrypt and decrypt the information being sent to and from the computer.The keys are used to verify that the information has not been modified or tampered with.

Lifecycle Difference

Certificates last longer than SSL keys. SSL certificates are obtained from Certification Authority, which can be renewed regularly by banks and businesses. SSL keys or session keys, on the other hand, are uniquely generated during the session and discarded when the session ends.

Read more here

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