Open Whisper Systems

Users of the iOS app called Signal can now encrypt their text messages and their phone calls for free.

Released on Monday, version 2.0 of Signal adds the ability to send free end-to-end encrypted messages to people across the world. Your messages can include text, pictures and videos, which are all encrypted to thwart people beyond the receiver from intercepting and deciphering the content.

What makes Signal unique is that owners of Apple's mobile devices can also send encrypted messages to people who have a compatible app installed on devices running Android, Google's mobile operating system.

You can send encrypted text messages to other iPhone users who have Signal and to Android users who run the TextSecure app on their phones. Further, you don't have to pay individual fees for each message. The new text message encryption feature comes on top of Signal's existing ability to encrypt mobile phone calls.

The power to encrypt your phone calls and text messages is a critical one for many people. Concerns about government snooping have increased since whistleblower and former NSA contractor Edward Snowden released confidential documents showing wide-scale data collection on the part of the agency. And more reports continue to surface.

The National Security Agency and its British counterpart, the Government Communications Headquarters, have both been accused of hacking into the internal network of SIM card maker Gemalto and stealing the encryption keys used to secure those cards. Citing documents released by Snowden, a report last month by The Intercept indicated that the agencies would've been able to tap into mobile phone voice and data communications from users around the world.

Another report released in February from security vendor Kaspersky revealed the existence of an organization called the The Equation Group, which was able to access the firmware of hard drives from Western Digital, Seagate, Toshiba, IBM, Micron and Samsung to plant spyware. The report noted that the group has ties to Stuxnet, a virus used to infect Iran's uranium enrichment facility. The NSA has been accused of planting Stuxnet, leading Reuters -- backed up by outside information -- to finger the agency as the source behind the hard drive spyware.

Apple's iMessage app does use encryption to secure your messages, but only between iOS devices and only over a proper data connection, The Intercept said.

Signal users can encrypt their phone calls to other iOS users using the same app. They can also encrypt those calls to Android users who run an app called Redphone, according to The Intercept. The Signal app itself is easy to use. You simply call or text the other person, and your conversation is automatically encrypted. You can also turn on screen security so no one can take a screenshot of your conversation.

"We cannot hear your conversations or see your messages, and no one else can either," Signal developer Open Whisper Systems said in a blog post on Monday. "Everything in Signal is always end-to-end encrypted, and painstakingly engineered in order to keep your communication safe."