OCSP vs CRL | Find the Real Difference between OCSP and CRL
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08/11/2022 by admin with 0 comments

OCSP and CRL : A Complete Comparison Guide

What is a Digital Certificate? 

A digital certificate is a virtual encryption protocol that demonstrates the genuinity of a server, device or organization via the utilization of PKI (Public Key Infrastructure) and cryptography. Authentication granted by a digital certificate assists organizations in ensuring that solely trustworthy sources can gain access to their servers.  Additionally, the legitimacy of other websites can also be established in the form of Secure Socket Layer (SSL).


The contents of a digital certificate include: the name of the user, the name of the corporation or organization and the IP address or serial number pertaining to a particular device. A duplicate of the public key is present in the certificate which is required to be compatible with the owner’s private key. Only if a match between the public and private keys is found, the verification process will occur. In order to certify the specifications of the requesting user, Certificate Authorities (abbreviated to CAs) publish a public key. 


In a nutshell, a digital certificate is necessary for encrypting procedures that lays a foundation of trust in transactions and interactions made online. The CA issued certificate provides evidence about the identity of the certificate owner. 


What is Certificate Revocation List?


The National Institutes of Standards and Technology defines a CRL or Certificate Revocation List as a collection of digital certificates that faced annulment by the CA before the assigned date of their expiration, as a result of which they are temporarily disabled. The certificates that are present in this list are no longer considered trustworthy by the CA. The CRL files contain the official signature of the CA in order to take precautions against tampering. 


CRL and Revoked Certificates


Generally, solely the devices of clients are required to verify if a CA has nullified a particular SSL certificate. Customers necessarily need to make inquiries so that they can be alerted in case a website is fraudulent and does not have any transparency. 


Certificate authorities are required to monitor the activities of the SSL certificates that they have revoked. The serial number of a revoked SSL needs to be added to the CRL. The CRL Distribution Points field contains the URL of every individual SSL that has been blacklisted for supervision. In order to check the status of revocation of a blacklisted SSL Certificate, the client is required to connect to the individual URLs and download the official CRLs that have been formed by the CA. . Among that list, the client will be able to locate the SSL certificate they are searching for. 


Online Certificate Status Protocol


In the modern era, surfing on the internet is a daily activity. There are several protocols implemented to enhance the speed of the browser and conduct other necessary tasks required for increased convenience of the user. OCSP is a procedure used by web browsers to ensure the validity of a security certificate.


One of the two widely used methods for preserving the protection of a website and other network components is OCSP (Online Certificate Status Protocol). It has almost entirely substituted the usage of CRLs for the purpose of checking  SSL Certificate revocation. Instead of having to download a long CRL list and searching for the necessary SSL URL amongst so many hyperlinks, OCSP provides a clearer and easier confirmation to a client whether a particular SSL certificate is indeed revoked or not. 


Understand OCSP Stapling 


By immediately placing the digitally signed and time-stamped OCSP awards on the web server, OCSP stapling enhances efficiency of the browser. The web servers can incorporate OCSP responses into the initial SSL handshake thanks to this “stapled” response. With this method, the user is not required to start a unique external connection to the CA. These stapled answers are updated by the CA at predetermined times.


Although OCSP is a useful tool for validating key certificates, it also has several serious drawbacks. Three main issues are brought up by the way OCSP is currently applied by browsers: privacy, performance, and a potential failure point. OCSP is currently in use, and you have the option to use OCSP Stapling, an improvised version of OCSP.


Web browsers consult with independent suppliers to determine the security certificate status. The connection to HTTPS will continue if the certificate is legitimate.


Difference between OCSP vs CRL


One of the two widely used methods for preserving the protection of a website and other network components is OCSP (Online Certificate Status Protocol). A certificate revocation list is an older technique that OCSP has replaced in some situations (CRL). The main drawback of CRL was that it required regular downloads of the latest updates in order to maintain the list up to date at the client end. On the other hand, OCSP circumvents this issue. For instance, OCSP makes a request for certificate status data whenever a user tries to access a server. The response from the server then states whether it was “current,” “expired,” or “unknown.” The protocol outlines the programming language for interaction between both the client application and the web server which has the status of the certificate (that is informed of that status).

In order to obtain sites for a brief amount of time before updating the certificate, OCSP grants a user with an expired certificate a leeway period. OCSP is essential to the prolonged certification of Secure Socket Layer (SSL) certificates and provides real-time status checks on security certificates. For instance, the browser normally does an OCSP check with the certificate authority (CA) that issued the SSL certificate when a user establishes an HTTPS connection with a web server. This is done to make sure that the certificate has not been revoked. However, this procedure can occasionally be the cause behind brief pauses in the SSL handshake.


Clearing Cache


Occasionally, it can be seen that an SSL certificate, even after having been revoked by its provider, remains in a client’s cache memory. Even though the suspicious certificate has been flagged as untrustworthy, hackers may still try to gain access to personal information through the cache reserved. 


Thus, it forms a fundamental requisite to clear CLR as well as the CLR address from the browser’s cache memory so that an alternative SSL certificate can replace the revoked one. Additionally, OCSP extensions need to be cleared off as well.


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