Lavabit Founder Waged Privacy Fight as F.B.I. Pursued Snowden DALLAS - One day last May, Ladar Levison returned home to find an F.B.I. agent's business card on his Dallas doorstep. So began a four-month tangle with law enforcement officials that would end with Mr. Levison's shutting the business he had spent a decade building and becoming an unlikely hero of privacy advocates in their escalating battle with the government over Internet security. The Guardian/Reuters The owner of the e-mail service said he closed it down after the government, in pursuit of Edward J. Snowden, sought untrammeled access to the protected messages of all his customers. Prosecutors, it turned out, were pursuing a notable user of Lavabit, Mr. Levison's secure e-mail service: Edward J. Snowden, the former National Security Agency contractor who leaked classified documents that have put the intelligence agency under sharp scrutiny. Mr. Levison was willing to allow investigators with a court order to tap Mr. Snowden's e-mail account; he had complied with similar narrowly targeted requests involving other customers about two dozen times. But they wanted more, he said: the passwords, encryption keys and computer code that would essentially allow the government untrammeled access to the protected messages of all his customers. That, he said, was too much. "You don't need to bug an entire city to bug one guy's phone calls," Mr. Levison, 32, said in a recent interview. In my case, they wanted to break open the entire box just to get to one connection. On Aug. 8, Mr. Levison closed Lavabit rather than, in his view, betray his promise of secure e-mail to his customers. The move, which he explained in a letter on his Web site, drew fervent support from civil libertarians but was seen by prosecutors as an act of defiance that fell just short of a crime. The full story of what happened to Mr. Levison since May has not previously been told, in part because he was subject to a court's gag order. But on Wednesday, a federal judge unsealed documents in the case, allowing the tech entrepreneur to speak candidly for the first time about his experiences. He had been summoned to testify to a grand jury in Virginia; forbidden to discuss his case; held in contempt of court and fined $10,000 for handing over his private encryption keys on paper and not in digital form; and, finally, threatened with arrest for saying too much when he shuttered his business. Spokesmen for the Justice Department and the F.B.I. said they had no comment beyond what was in the documents. Mr. Levison's battle to preserve his customers" privacy comes at a time when Mr. Snowden's disclosures have ignited a national debate about the proper limits of surveillance and government intrusion into American Internet companies that promise users that their digital communications are secure. Much of the attention has been focused on Internet giants like Microsoft and Google. Lavabit, with just two employees and perhaps 40,000 regular users, was a midget by comparison, but its size and Mr. Levison's personal pledge of security made it attractive to tech-savvy users like Mr. Snowden. While Mr. Levison's struggles have been with the F.B.I., hovering in the background is the N.S.A., which has worked secretly for years to undermine or bypass encrypted services like Lavabit so that their electronic message scrambling cannot obstruct the agency's spying. Earlier in September, The New York Times, ProPublica and The Guardian wrote about the N.S.A."s campaign to weaken encryption. Mr. Levison's case shows how law enforcement officials can use legal tools to pry open messages, no matter how well protected. Mr. Levison said he set up Lavabit to make it impossible for outsiders, whether governments or hackers, to spy on users" communications. He followed the government's own secure coding guidelines, based on the N.S.A."s technical guidance, and engineered his systems so as not to log user communications. That way, even if he received a subpoena for a user's communications, he would not be able to gain access to them. For added measure, he gave customers the option to pay extra to encrypt their e-mail and passwords. Mr. Levison, who studied politics and computer science at Southern Methodist University, started Lavabit in April 2004, the same month Google rolled out Gmail. To pay his bills, he worked as a Web consultant, helping develop Web sites for major brands like Dr Pepper, Nokia and Adidas. But by 2010, the e-mail service had attracted enough paying customers to allow Mr. Levison to turn to Lavabit full time.