I’m old enough to remember when encryption technologies not half as powerful as the iPhone’s were considered weapons of war. As recently as 1992, Tim Cook’s stance on strong crypto would have put him on the wrong side of the U.S. Munitions Act.

But that was before the rise of the personal computer, the spread of the Internet, and the release in 1991 of a program called PGP, for Pretty Good Privacy.

PGP made modern public-key encryption—the kind Apple uses—freely available to anyone with secrets to keep, from brokerage firms to terror cells. The U.S. tried to outlaw the program, but its author, a peace activist named Phil Zimmerman, published the source code in book form and successfully argued that its distribution—at least within the U.S.—was protected by the First Amendment.

Pressured by commercial interests, Congress lifted the restrictions of the Munitions Act in 1992, but strong crypto—and the ability to crack it—lost none of its strategic significance.

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In World War II, it was Alan Turing’s primitive computer that cracked the Nazi’s coded messages to submarine commanders, giving the Allies the edge they needed to win the Battle of the Atlantic. Today, the most powerful code-breaking supercomputers are in the hands of the National Security Agency. If it weren’t for Edward Snowden’s revelations of NSA abuses, Apple might never have written into iOS the barriers to brute force attacks that are causing the FBI such headaches.

A federal court has ordered Apple aapl to write a version of iOS with those barriers removed. Tim Cook has refused, publicly and repeatedly. That would set a dangerous legal precedent, he says, and compromise the security of hundreds of millions of devices. Besides, the bad guys who know what they’re doing already have the latest version of PGP.

Meanwhile, according to The New York Times, Apple has begun developing new security measures that would make it impossible for the government to break into a locked iPhone using the tools the FBI has ordered Apple to build.

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Thus begins a new round of the kind of cat-and-mouse games the technology seems to encourage—games that tend to be won by whoever has the best software engineers and the funds to support them.

President Obama, who resisted pressure to rein in private use of powerful encryption, may regret giving the FBI the green light to go after Apple.