As funny as it sounds: iMessage. The only crypto-related problem with iMessage's encryption is that Apple controls the key servers. -- http://techcrunch.com/201

As funny as it sounds: iMessage. The only crypto-related problem with iMessage's encryption is that Apple controls the key servers. -- http://techcrunch.com/2014/02/27/apple-explains-exactly-how-secure-imessage-really-is/ http://techcrunch.com/2014/02/27/apple-explains-exactly-how-... Besides, it is not available for non-Apple devices. TextSecure/Signal has a robust crypto system, and they are working on multi-device support.