That was my motivation for publishing the metadata I received from T-Mobile. Together with Zeit Online, the online edition of the weekly German newspaper Die Zeit, I published an infographic of six months of my life for all to see. With these 35,830 pieces of data, you can follow my travels across Germany, you can see when I went to sleep and woke up, a trail further enriched with public information from my social networking sites: six months of my life viewable for everybody to see what exactly is possible with “just metadata.”

Three weeks ago, when the news broke about the National Security Agency’s collection of metadata in the United States, I knew exactly what it meant. My records revealed the movements of a single individual; now imagine if you had access to millions of similar data sets. You could easily draw maps, tracing communication and movement. You could see which individuals, families or groups were communicating with one another. You could identify any social group and determine its major actors.

All of this is possible without knowing the specific content of a conversation, just technical information — the sender and recipient, the time and duration of the call and the geolocation data.

With Edward J. Snowden’s important revelations fresh in our minds, Germans were eager to hear President Obama’s recent speech in Berlin. But the Barack Obama who spoke in front of the Brandenburg Gate to a few thousand people on June 19 looked a lot different from the one who spoke in front of the Siegessäule in July 2008 in front of more than 200,000 people, who had gathered in the heart of Berlin to listen to Mr. Obama, then running for president. His political agenda as a candidate was a breath of fresh air compared with that of George W. Bush. Mr. Obama aimed to close the Guantánamo Bay detention camp, end mass surveillance in the so-called war on terror and defend individual freedom.

But the senator who promised to shut Guantánamo is now a second-term president who is still fighting for its closure. And the events of the past few weeks concerning the collection of metadata and private e-mail and social-media content have made many Germans further question Mr. Obama’s proclaimed commitment to the individual freedoms we hold dear.

DURING Mr. Obama’s presidency, no American political debate has received as much attention in Germany as the N.S.A. Prism program. People are beginning to second-guess the belief that digital communication stays private. It changes both our perception of communication and our trust in Mr. Obama.

Even as a Green Party politician, I wasn’t impressed with Mr. Obama’s focus on fighting global warming. While his renewed enthusiasm is appreciated, it served as a distraction from the criticism he is currently facing for allowing invasive state surveillance. He cannot simply change the subject.