






In 1997, for instance, the Senate debated technology that would require encryption-makers to  build in a backdoor for law enforcement. FBI director Louis Freeh argued that "Uncrackable encryption will allow drug lords, spies, terrorists and even violent gangs to communicate about their crimes and their conspiracies with impunity. We will lose one of the few remaining vulnerabilities of the worst criminals and terrorists upon which law enforcement depends to successfully investigate and often prevent the worst crimes."

So why hasn't that happened? Because even uncrackable encryption can be circumvented, says Blaze. Cell phones, for instance, the major target of wiretapping, have their wireless signals encrypted by default. But law enforcement agencies aren't likely to be intercepting calls out of the air and trying to decode them. Far simpler to go to AT&T, Verizon, T-Mobile or Sprint and demand real-time access to the decoded data.

Encrypted VoIP calls pose a different scenario, and technologies like Phillip Zimmermann's Zfone may pose more of a threat to law enforcement. But even those cryptographic safeguards can be skirted in other ways, potentially by exploiting vulnerabilities at the endpoints, when the data is decrypted. "The endpoints of encryption systems are programmable computers, and they almost always have security flaws," says Blaze.

Privacy- and security-focused encryption advocates (like Symantec, which just purchased encryption firm PGP for $300 million) will have to ponder just how law enforcement got around the encryption in the one case where it was "encountered." Does the FBI, for instance, have secret technology for cracking the public key encryption used in private emails?

But a more fundamental question for cypher-geeks may be why, in 99.99% of cases,  law enforcement doesn't even consider encryption a barrier.

Here's the complete report, including a county by county breakout of wiretaps and which resulted in the most arrests (Two cases in Maricopa County, Arizona top the list).Annual Report on Wiretapping in the U.S.