Cellcrypt released a version of its voice encryption software for Apple's iPhone on Tuesday, adding to its portfolio of software to prevent eavesdropping on calls.The product, called Cellcrypt Mobile for iPhone, works with iOS4 on Apple's iPhone 3GS and iPhone 4. It is one of two voice encryption applications listed in the App Store, although there are other voice encryption applications for the iPhone platform from vendors such as Goldlock and SecurStar.The iPhone application works in the same way as Cellcrypt's products for other platforms. It's a VOIP (voice over IP) application that uses either Wi-Fi or an operator's data channel on either GPRS, EDGE, 3G or satellite networks to transmit voice.Both the caller and the recipient must have Cellcrypt installed in order to encrypt the call. The iPhone version is interoperable with other Cellcrypt software for platforms including Symbian, Android and Blackberry, said Ian Meakin, Cellcrypt's vice president of marketing.Cellcrypt uses public key cryptography, and each phone running its software has its own private key stored only on the device. When a call is initiated, the two devices exchange a secret session key, which is then erased when the call ends.Voice data is then double encrypted first using a 256-bit RC4 algorithm and then again with a 256-bit AES algorithm, Meakin said. The heavy encryption can cause up to a 1.5 second delay using the slower GPRS networks, varying somewhat depending on available bandwidth and network traffic. Over Wi-Fi, latency can be as low as 150 milliseconds, which is unnoticeable to callers. Meakin said tests have shown that latency has been less on the iPhone due to its speedy processors.Cellcrypt Mobile meets the U.S. government's 140-2 Federal Information Processing Standards, which means it can be used by government employees for certain classifications of information.Cellcrypt recently raised the price of an annual subscription from US$1,500 to $1,600. With that change, Cellcrypt is allowing users to change devices without requiring customers to buy another license. Users can now also install Cellcrypt's software on another device, Meakin said.