Maria Dryfhout, 123RF

What's left of TLS

Incomplete Security

Article from ADMIN 15/2013

By Hanno Böck

Numerous attacks have rocked the security of SSL/TLS encryption in recent years. Newer standards would remedy this, but they are not widely used.

The TLS protocol (formerly SSL) is the basis of secure communications on the Internet. Every website that is accessed via HTTPS uses TLS in the background. However, TLS is getting on in years. Many design decisions were found to be unfavorable after extensive analyses, and the security of the protocol has been questioned. The reactions to these findings have been mostly patchwork. Small changes to the protocol have prevented attacks so far, but the problem is fundamental.

A Brief History of SSL

SSL (Secure Socket Layer) was originally developed by Netscape. In 1995, when the World Wide Web was still in its infancy, the former monopolist browser released the SSL encryption protocol version 2.0 (SSLv2). Version 1 existed only internally in Netscape. Numerous security vulnerabilities were discovered in SSLv2 after a short time.

SSLv2 supported many encryption algorithms that were already deemed insecure at the time, including the Data Encryption Standard (DES) in its original form with a key length of only 56 bits. The 1990s, when SSLv2 was being developed, were the hot phase of the "Crypto Wars." Strong encryption technologies were forbidden in the United States. Many states talked about only allowing strong encryption under state control – with a third key, which would be deposited with the secret service.

After that, Netscape published SSLv3 to fix at least the worst of the security problems. Although SSLv2 is only of historical importance today and has been disabled by virtually all modern browsers, its successor is still in use and you can still find web servers that only support SSLv3.

It was not until later that SSL was standardized. This process also involved renaming it to TLS (Transport Layer Security), which caused much confusion. In 1999, the IETF standardization organization published the TLS protocol version 1.0 in RFC 2246 (TLSv1.0). The now 14-year-old

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