Silence on the Wire

Getting More Out of Sequence Numbers

Naturally, it is important to be able to tell the good ISN-generator implementations from the bad, both for quality assurance and for security testing. Until recently, the usual approach to assessing the quality of generated initial sequence numbers relied either on source-code analysis or on certain one-dimensional tests of the bit stream of subsequent ISNs to estimate the entropy carried by each bit of the output. The former is often complex and costly, is prone to errors, and is not always possible (in the absence of publicly available source code for a specific system). The latter lacked the ability to capture more subtle sequence dependencies and other characteristics of a generator in a reliable and readable ...