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Text Secure by Open Whisper Systems (OWS) is the messaging sibling of OWS' encrypted voice app RedPhone, and offers encrypted SMS, MMS and instant messaging.
Until recently, Text Secure was purely for encrypted SMS and MMS, but OWC recently introduced new features that bring it up to par with IM apps that communicate over data networks. Users can create private chat groups with the same end to end encryption previously offered with TextSecure SMS chats.
OWS compares it to an encrypted version of Apple's iMessage. TextSecure is a normal SMS/MMS app when communicating with non-TextSecure users, but sends messages encrypted over a data network when both are TextSecure users.
The app is not available for Windows but it's coming soon to iOS. OWS' chief engineer Moxie Marlinspike recent worked with the CyanogenMod team to bring it to the popular custom ROM, which means that Android and soon iOS users can connect securely with friends running it.
As a social app, Text Secure faces the usual privacy challenges in building a social network through find friend features.
"The simplest way to calculate the intersection of registered users and device contacts is to upload all the contacts in the address book to the service, index them, reverse index them, send the client the intersection, and subsequently notify the client when any of those contacts later register," Marlinspike noted in a recent post on the find friend conundrum.
'Encrypted bloom filters' could allow that process to happen privately on the end-user's device, but the file would be impractically large for TextSecure's user base of 10 million, according to Marlinspike.
Meanwhile, the finite possible mobile numbers meant hashes of them could be easily guessed.
"For RedPhone, our user base is still manageable enough (for now) to use the bloom filter technique. For TextSecure, however, we've grown beyond the size where that remains practical, so the only thing we can do is write the server such that it doesn’t store the transmitted contact information, inform the user, and give them the choice of opting out," Marlinspike noted.
BoxCryptor, a German company, has Android and iOS apps that help the user encrypt files on the fly before uploading to a cloud. The app supports sending encrypted files to Dropbox, Google Drive, Microsoft OneDrive Box, and others using WebDAV.
The free app offers encryption and support for one provider. The paid and enterprise versions support multiple providers.
BoxCryptor plans to release encryption its app for Windows Phone, Windows RT, and Blackberry 10 by the end of this quarter.
On the spectrum of privacy apps, Telegram sits somewhere between TextSecure and Snapchat and apparently has benefited big-time from Facebook's acquisition of WhatsApp.
Telegram has the usual self-destruct option for messages, and has promised no ads, no subscription fees, and no outside investment — except for a generous donation that helped kick it off.
The cloud service hopes its combination of 'normal' chats and 'secret' chats bridge the knowledge gap among most users about security.
Telegram claimed to have gained five million new users on the day Facebook announced its WhatsApp acquisition.
Secret chats use end-to-end encryption and are not stored on Telegram's servers and can only be accessed from the devices they were sent to or from.
Telegram was bankrolled by VKontact founders and brothers Pavel and Nikolao Duroy, however it says it's a Berlin headquartered company with no connections to Russia.
Nikolao developed a custom, open protocol called the MTProto Mobile Protocol and Pavel in December offered $200,000 in Bitcoin to any hacker who could break it. The competition closed on March 1 without a winner and it's planning on launching a new competition soon.