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General Questions

What is ZRTP?

ZRTP is a cryptographic key-agreement protocol to negotiate the keys for encryption between two end points in a Voice over Internet Protocol (VoIP) phone telephony call based on the Real-time Transport Protocol. It uses Diffie–Hellman key exchange and the Secure Real-time Transport Protocol (SRTP) for encryption. ZRTP stands for “Zimmermann Real-time Transport Protocol” and was developed by Silent Circle’s own, Phil Zimmermann.

As VoIP grows into a replacement for the PSTN, we will absolutely need to protect it. VoIP is far more vulnerable to interception than the PSTN. A PC on your office network can unknowingly host spyware that can intercept your corporate VoIP calls and store and organize them on a hard disk for convenient browsing by criminals half a world away, giving them trade secrets and insider trading opportunities.

The Internet is not a safe medium to carry our phone calls. This technology has social benefits. It has the power to change our lives, enabling us to have a private conversation any time we want with anyone, anywhere – without buying a plane ticket.

mOS comes with PaX patched kernel.PaX is a patch for the Linux kernel that implements least privilege protections for memory pages. The least-privilege approach allows computer programs to do only what they have to do in order to be able to execute properly, and nothing more. PaX was first released in 2000.

PaX flags data memory as non-executable, program memory as non-writable and randomly arranges the program memory. This effectively prevents many security exploits, such as some kinds of buffer overflows. The former prevents direct code execution absolutely, while the latter makes so-called return-to-libc (ret2libc) attacks difficult to exploit, relying on luck to succeed, but doesn’t prevent overwriting variables and pointers.

PaX is maintained by The PaX Team, whose principal coder is anonymous.

Address space layout randomization (ASLR) is a computer security technique involved in protection from buffer overflow attacks. In order to prevent an attacker from reliably jumping to, for example, a particular exploited function in memory, ASLR randomly arranges the address space positions of key data areas of a process, including the base of the executable and the positions of the stack, heap and libraries.

We own all our servers which are held in multiple locations each with multiple backups in other locations – we store these in countries which follow strict data privacy laws, who also don’t work with other organizations out with their own jurisdiction. We will never reveal the locations and have proxies in place to protect this also.

Sometime you will see this message if you or your contact close an active chat session and the other person leaves it open.
This will then causes a new key to be generated only on one end of the session meaning the other person cannot receive the new message “Hence why it says this message is unreadable”
To fix this both of you have to press your Green Padlock on the bottom left and select ” Stop Encryption” and then press ” Start Encryption” then message your contact as normal and you will find everything back in sync and working.