Speaking in a packed Stanford University lecture hall, Felten said he thinks he will eventually win the rights to publish his work, which so far has been quashed by the entertainment industry.
"The music industry was seeking control over what we could write in our paper," Felten said. "That's a dangerous precedent."
The Secure Digital Music Initiative (SDMI)--a group working to protect digital material from theft--issued a hacking challenge last year, asking participants to try to break some watermark technology it was considering using. A digital watermark places a unique bit of code into a file that is theoretically difficult to remove without damaging the quality of the sound or image.
Felten entered the contest but withdrew after learning that contest rules prohibited him from discussing his findings. Instead, he and his colleagues set out to work on the project independently.
Shortly before he was scheduled to give a presentation last month detailing how he and his colleagues cracked the watermarks, Felten buckled under pressure from the SDMI, which told the academic team it risked violating federal copyright laws if its findings were made public.
Once Felten backed down, though, the SDMI said it never intended to sue the professor or restrict academic speech, an assertion many are questioning.
Felten wouldn't speculate Thursday about the next step in releasing his watermark research. Although he didn't specifically explain how he cracked some of the watermarks, he said that once someone determines how the watermarks work it's easy to remove them.
"Given all of this, it's not clear that watermarks, at least in the style that SDMI wanted to do it, can work at all," he said.
Felten also said computer scientists shouldn't be the only ones worried about their speech being stifled.
"If it happened to us, it could happen to other disciplines as well," he said. For example, he said in the future that a literature professor could be prevented from giving an analysis of a book, in the same way his group was prevented from discussing an analysis of technology.
Felten has been something of a techno-political activist in recent years. As a government witness during the Microsoft trial, he testified that he had designed a program that would remove the browser from Windows without damaging the operating system. The software giant asserted the products were so intertwined that it wasn't possible.
The programmer also took sides in the DeCSS case, a lawsuit brought by the movie industry against a hacker publication for posting code that theoretically could be used to crack DVD security. Felten was one of a group of crackerjack programmers who signed on to a brief in favor of 2600 magazine. He and his colleagues argued that computer code is free speech and should not be restrained.
Felten also testified during that trial, warning somewhat prophetically that if the industry was going after hackers, he could be next.