Why is SSL 3.0 deprecated?

What are the different versions of SSL?

What are the differences between the versions of SSL? Why are they different? What are the key differences between them? The first and most important difference is the underlying protocol. There are two main types of SSL: SSLv2 and SSLv3.

SSLv2 has been deprecated since 2024. SSLv3 was developed and standardised by the IETF in 2024. As a result, SSLv2 does not support some of the newer features that SSLv3 offers. For example, SSLv2 does not support Server Name Indication (SNI).

What is Server Name Indication? SNI is a mechanism for specifying which hostname a client should connect to. For example, if the client wants to connect to www.google.com then it tells the server connect to www. If it is connecting to a different server then it tells the server connect to www.gmail.

SNI was introduced in 1999 as a method for allowing multiple different hosts on a single IP address to share the same certificate. You could have one web server that is serving the pages for both www.com and www.com, but it would be a waste of resources if both of those sites needed to run the same certificate.

SNI is also used for server-to-server communications. A common use-case is to serve the content of your site via HTTPS while redirecting a user who tries to access it via HTTP to the secure site.

The following diagram shows the different protocols: How do I tell whether my server is using SSLv2 or SSLv3? On your webserver, there are two main ways to tell whether your server is using SSLv2 or SSLv3. The first is to use the command openssl sclient -connect IPADDRESS:PORT and look at the output. If the version is SSLv2 then you will see the text SSLconnect: before/during handshake. If you don't see this then you are using SSLv3.

You can also check your Apache error logs or the logs of your web browser. Many web browsers will warn you if your web server is using SSLv2.

What does SSLv3 offer?

Why is SSL 3.0 deprecated?

I'm not the only one who thinks that SSL 3.

0 is a waste of server CPU cycles and bandwidth. It was a bad idea from the start. And yet, there are still many servers running SSL 3.0, as evidenced by the many websites with warnings about SSL 3.0 being insecure:

Why does this still happen? I'd guess it's because of lack of knowledge about how to run a secure server. A lot of sysadmins never upgrade their servers from SSLv2, thinking that they are running SSL 3.0 (which, in reality, they are not). They also use outdated tools, like telnet, which have known vulnerabilities.

If you are running a server, don't be a slave to marketing materials and best practices. In the end, it doesn't matter if you support SSL 3.0 or not, your users are not going to care. The world is moving forward to TLS 1.2, so if you don't upgrade your server to support it, you are simply making your users more vulnerable. If you don't want to make your users less secure, upgrade your server to SSL 3.

One way to address this is to write your own script that auto-upgrades servers that are using SSL 3. This may sound scary, but really, this shouldn't be too hard to do. After all, it's just converting strings and hex values.

Here is what I would do: Download the latest OpenSSL source code Find the C source code for the function you wish to modify (eg ssl3getmessage) Look at the code for the function calls that create a new SSL 3.0 session Find the call that adds the certificates to the session Read the man page for that function, and find how it handles the SSL 3.0 certificates Return the list of new certificates as well as the new session state from the man page

In other words, we're going to do an in-place upgrade of servers. We don't need to remove SSL 3.0 entirely, we just need to change the way SSL 3.0 works. And while we are at it, we might as well fix a few other bugs in the SSL 3.0 code.

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