Today on CNN they conducted an interview with a career criminal, who spoke by Skype on condition of anonymity. It occurred to me that, if Skype uses digital watermarking to embed identifying information in the audio stream, then this criminal has potentially blown his cover, at least to Skype and to any other entity with knowledge of the watermarking technique.
Skype is, of course, a closed-source program that is known to surreptitiously access third-party configuration files (for reasons that may or may not be nefarious), and it is claimed that law enforcement agencies have the ability to eavesdrop on Skype conversations. However, I don't know whether anyone has ever alleged or investigated claims that Skype uses imperceptible audio watermarking to covertly embed identifying information, such as the originating Skype account ID, MAC address, IP address, operating system details, etc.
Have there been any leaks or admissions by Skype confirming their use of such watermarking? If not, has anyone attempted to use technical methods to detect the presence and/or contents of such watermarking?