CALIFORNIA, USA: Twitter has acquired a start-up company that makes software to improve security and privacy for smartphones and other mobile devices.

With its acquisition of Whisper Systems, Twitter gains technology to bolster security of its fast-growing microblogging service and gets a pair of highly-respected experts in the field of online security.

Whisper Systems was co-founded last year by security experts Moxie Marlinspike and Stuart Anderson.

"The Whisper Systems team is joining Twitter starting today," Twitter said in an emailed statement on Monday. "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 and Stuart onboard."

Twitter did not disclose a price for the deal and declined to comment beyond its statement.

Twitter, which has more than 100 million active users, allows people to send short, 140-character, messages to groups of followers.

The service has become a popular communications tool for celebrities, politicians and businesses. It has also played a role in several geopolitical events, such as the past year's uprisings in the middle east, by allowing dissidents to organize and communicate.

But some privacy advocates have warned that certain governments also have used Twitter to help monitor dissidents and activists.

Whisper Systems offers programs that scramble data, voice conversations and text messages on mobile devices that use the Android operating system, so that the information cannot be accessed by hackers.

Marlinspike is highly respected in the security community, having gained notoriety for discovering high-profile vulnerabilities in systems that encrypt data over the Internet and wifi net