It was 21 years ago this spring that hundreds of thousands of students flooded the streets of Beijing, Shanghai, and other Chinese cities to protest communist repression and call for greater freedom and democratic reforms. Those amazing demonstrations generated intense global interest — interest the regime tried to quell by blocking international TV transmissions, ordering Western networks to halt their coverage, and arresting several journalists.

But the government overlooked the then relatively new communication technologies of cellular phones and fax transmissions. As the Newseum’s Sharon Shaheed described it in a retrospective last year, “Reporters got around the ban by reporting by mobile telephone. Students in China’s prodemocracy movement kept the news flowing by fax machines and electronic mail connections. Technology managed to open Chinese repressions to the world, despite government censorship.” The same technology enabled the world to respond, buoying the protesters with invaluable moral support.

In the wake of the Chinese uprising and the fall of the Iron Curtain later that year, many voices extolled the power of technology to advance liberty and undermine authoritarian regimes. Two decades later, many are still hailing the ability of information technology to produce greater freedom — only the technical innovations being celebrated now are the Internet, text messaging, and social media applications such as Twitter and Facebook. Tweets by the thousands fueled the “Green Revolution” set off by last year’s elections in Iran, and prodemocracy activists from Vietnam to Venezuela are using the Internet to denounce repression, expose government corruption, and champion human rights. “The Internet is God’s present to China,” the prominent dissident Liu Xiaobo exulted a year ago. “It is the best tool for the Chinese people in their project to cast off slavery and strive for freedom.”

If only that were true. If only the miracles of high-tech communication really were a silver bullet against dictatorship and government brutality. But fax machines didn’t prevent China’s rulers from sending in tanks to crush the 1989 democracy movement at Tiananmen Square, and Twitter hasn’t weakened the mullahs’ grip on power in Iran. As for Liu Xiaobo, he was convicted of “subversion” this past December and sentenced to 11 years in prison.

For all the wonders it makes possible, information technology is only a tool, and like all tools it can be used to promote the cause of freedom, or to oppose it. That was the sobering theme of a conference on cyber-dissidents organized in Dallas last week by the George W. Bush Institute in conjunction with the human-rights organization Freedom House. The conference brought together online dissidents from an array of unfree or authoritarian countries — China, Syria, Venezuela, Russia, Cuba, and Iran — as well as experts on Internet strategy, nonviolent resistance, and international relations.

It is always inspiring to encounter individuals who jeopardize their safety and freedom to speak truth to power, and the dissidents gathered on the campus of Southern Methodist University were no exception. Ahed al-Hendi, a young antigovernment activist seized by the Syrian mukhabarat — the secret police — as he was blogging in a Damascus Internet café, spent 34 days in a 3-by-5-foot jail cell. The Russian dissident Oleg Kozlovsky (who was grounded in Europe and joined the conference via Skype) has been repeatedly arrested and was even drafted by the Russian army in 2007 in order to thwart his prodemocracy activities. As former President Bush put it in opening the conference, these “are people who refuse to take the lack of freedom for granted.”

The speakers traded war stories and discussed ways to use cyber-technology to rally supporters and share intelligence. But running through the whole program was the Dickensian sense that today’s dissidents are living in the best of times and the worst of times: The social-media explosion makes it easier for champions of freedom to organize opposition and get information to the outside world, yet the very same online technology arms repressive governments with sophisticated new methods of censorship, surveillance, and disinformation.

Far from ushering in a golden age of democracy, remarked the Bush Institute’s James K. Glassman, a former undersecretary of state for public diplomacy, the Internet era has coincided with a “freedom recession.” Interactive Web 2.0 applications have facilitated the rise of “Authoritarianism 2.0.”

The Internet, in short, will not set men and women free. It is, rather, just the latest arena in which those who yearn for liberty must battle for it — and in which the outcome is never guaranteed.