Elana Kehoe doesn't like the idea of governments and hackers reading her e-mail as it traverses the Internet. So a few weeks ago, she installed a tool to scramble her messages. But she's having trouble using Pretty Good Privacy encryption. She knows of only four other PGP users, including her husband, Brendan. That means everything else goes through regular e-mail, which is as private as sending a postcard. . . .
Elana Kehoe doesn't like the idea of governments and hackers reading her e-mail as it traverses the Internet. So a few weeks ago, she installed a tool to scramble her messages. But she's having trouble using Pretty Good Privacy encryption. She knows of only four other PGP users, including her husband, Brendan. That means everything else goes through regular e-mail, which is as private as sending a postcard.

KEHOE HAS TRIED to persuade friends to install the free software, too, but they couldn't be bothered. "Since I don't know that many people who use PGP, I don't know what I can fully do with it now," said Kehoe, a Dublin, Ireland, resident visiting Cambridge for a computer conference this past week.

Her plight reflects a larger problem with e-mail security. Fewer than 10 million people use PGP, the most popular method for encrypting e-mail. That's out of a worldwide Internet population approaching 400 million.