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      • Perfect Forward Secrecy - Protecting the gateway to your world

        Jul 31 2014, 10:40 AM

        by Robert Lin 0

        Remember the movie "The Truman Show", where Jim Carrey played the main character of a TV show that chronicled the life of a man who was initially unaware that he was living in a constructed reality television show, broadcast around the clock to billions of people around the globe. Imagine that your organisation is chronicled the same way. Every online transaction, secured or not.

        That's what Heartbleed can do.  Fortunately most systems using OpenSSL libraries have been patched (hopefully) to counter this. What if there is another way that this can be done. That this could be happening right now, on a  daily basis and that this is not a vulnerability, but is actually how most clients connect to organisations during SSL/TLS negotitaions for the past decade?

        Fristly have a look at how SSL/TLS handshake works. 

        Consider this scenario:

        A script kiddie downloads Wireshark and uses it to track network activities within your organisation. Entire transations are recorded, including SSL sessions.  Several years later, after gaining much experience, he can now gain access to the servers and the expired Private Key pairs that were once used to encrypt these sessions. These sessions were encrypted with RSA key exchange. He emails the CSO, "I know what you did last summer".

        OK. A bit too dramatic and over the top, but perfectly possible. This is the flaw (not vulnerability) when using RSA Key Exchange in SSL/TLS negotiations without proper Key Management. As each session is related to the RSA private key used, recorded sessions can be decrypted later.

        An alternative to the RSA key exchange is to use another algorithm, Diffie-Hellman, which creates sessions that are not associated with the private key. Even if the session information is recorded there is no easy way to decipher the computations. With proper Diffie-Hellman implementation, encrypted information cannot be deciphered in the future. This is called Forward Secrecy.

        To see how Perfect Forward Secrecy can be be achieved, ready your coffee, get your thinking cap on and start reading the document attached. 

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      • Think you're safe? Think again - SSL Attack Survey

        Aug 05 2014, 1:21 PM

        by Robert Lin 0

        Look! I have a lock, I see https://, I even see the Green Bar, I believe I have protected my server and the clients connecting to our services from attackers now. I can't start increasing security and block clients to my site by disabling SSLv3, MD5 or RC4. I'll be losing customers and profit! I can accept a weaker security as long as user traffic and profit are not affected.

        Performance vs Security is a constant struggle between security experts and management. When it comes to SSL it is no different. Do we allow as many clients to access our site as possible, or do we block all the weak connectivities. There has been numerous studies on this, so I won't go into it here. As a SSL security expert, allow me to take sides this time. Allow me to provide some more gear for us to convince our management why SSL security is more important and how we can migitate the risks without affecting performance or traffic too much.

        Last year September a comprehensive survey was done by iSECPartners,Inc on the various vulnerabilities with the SSL/TLS technology.

        Have a look: Attack on SSL

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      • SSL Ciphers - Beyond Private key and Certificate

        Oct 20 2017, 8:35 PM

        by Robert Lin 2

        Today SSL is an integral part of online businesses and any secured communication. It is however not an area that many system administrators or security experts are comfortable with. For most administrators the correct installation of the private key and its corresponding certificate is sufficient. As long as the green bar, the padlock, or https:// can be seen during the SSL/TLS negotiation, both the administrators and their clients trust that the connectivity is secure.

        However many security flaws and vulnerabilities have been discovered in the recent years. From the server side there is the infamous Heartbleed bug or CCS injection - CVE-2014-0224, side-channel attacks such as Beast, Lucky 13, Crime or BREACH, and others (SSL Attack Survey).  It is not sufficient to just have a correct installation of the private key and certificate pair on the server. Beside patching up server libraries and client applications, additional control to SSL/TLS negotiations need to be applied. One of those control mechanisms is selecting the right cipher suite.

        The strength of an SSL/TLS negotiation depends not only the size of the private key or certificate. As of 2014, the recommended minimium key pair size is 2048 bit, however this does not guarantee maximum encryption sessions. During SSL/TLS handshakes, the agreement of what cipher suite to use determines if the negotiation will be using SSL or TLS protocols. It also determines the key exchange and encryption algorithms. If the agreed encryption level between the client and the server is low, the SSL/TLS session will still be vulnerable. For a system to be truly secure, strong cipher suites are required.

        To address this issue, a project was initiated. The result, "SSL/ TLS Cipher Suite Analysis and strong Cipher Enablement" is included in this blog.

        The purpose of this research is to provide an implementation process to set up a strongly secured SSL/TLS system by viewing the available cipher suites present in a system, recognizing the strength and weakness of the different ciphers and choosing the most applicable cipher suite.

        Note:  The configuration examples given in this document do not represent the complete or best set of strong ciphers to use. Depending on the various security policies and business requirements, the examples given in the document may not apply .

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