Twitter has removed the RedPhone from the ears of Middle East protesters.

Twitter has acquired Whisper Systems, a small outfit founded by well-known internet-security expert Moxie Marlinspike that aims to provide “enterprise-grade” security for Android phones and tablets.

At first blush, the move is a bit baffling. Twitter, the quintessential consumer internet service, would seem to have little need for a company that has revamped Android security from the ground up for business use. But the micro-blogging site may simply be acquiring Whisper Systems for its talent — including Marlinspike, who serves as the startup’s chief technology officer, and roboticist Stuart Anderson — and the two companies do have a certain affinity. Both pride themselves on the support they’ve provided to protesters in the Middle East.

Security and privacy guru Chris Soghoian believes Twitter may have brought Moxie Marlinspike into the fold because the micro-blogging site has developed a reputation for not having the best security. Marlinspike is an expert in SSL (secure sockets layer) encryption, and Twitter — which has yet to turn on SSL by default for all users — could use his skills to lock down its services and make life harder for phishers.

“The Whisper Systems team is joining Twitter starting today,” Twitter said in a canned statement. “As part of our fast-growing engineering team, they will be bringing their technology and security expertise to Twitter’s products and services. We’re happy to have Moxie Marlinspike and Stuart Anderson onboard.”

In a blog post, Whisper Systems said it would take down its cloud-based encrypted backup service, Flashback, in one month’s time, giving people time to move their data elsewhere during the transition period. But its RedPhone — a free call-encryption service that prevents eavesdropping — will be taken offline immediately.

In a brief email to Wired, Marlinspike said that RedPhone has been taken down “temporarily.”

RedPhone was specifically designed for those involved in the Egyptian revolution earlier this year, and Marlinspike saw it as something that could serve similar movements across the globe. “[RedPhone] is targeted just for Egypt, but sets the stage for worldwide support,” he told Wired in February. “Hopefully with stuff happening in Egypt it kind of steps things up [regarding distribution to other countries].”

Soghoian, for one, laments the loss of the device. “I understand that’s the normal thing in Silicon Valley, where everything gets shut off when an acquisition is made,” he says. “But RedPhone isn’t some app that helps you find the nearest ice cream store. [Whisper] specifically targeted helping people under repressive regimes. Just shutting it off with no warning to users puts the people in a very dangerous position, especially in places like Egypt where they’re having elections today.”

Soghoian hopes that Twitter will open source the Red Phone, and Whisper Systems indicates that the code will survive in some form. “The Whisper Systems software as our users know it will live on,” the blog post read. Considering Twitter longtime support for the Arab Spring uprisings, we can only assume that the RedPhone will return.

Additional reporting by Robert McMillan.

Photo: Palestinians, one talking on a mobile phone, sit in a tent, while Arab League Secretary General Amr Moussa of Egypt, not seen, delivers a speech, during a visit to the area of Abed Rabbo, damaged during the offensive Israel launched in late 2008 to early 2009, eastern Gaza Strip, Sunday June 13, 2010. (AP Photo/Lefteris Pitarakis)

Update: This story has been updated with a statement from Twitter.