From The SAGE Encyclopedia of Business Ethics and Society
Operation Bull Run
NSA Operation Bull Run commenced sometime around 2000 and ended in 2010. This NSA program has stimulated criticism of the Internet encryption operation. NSA capabilities now include the power to break numerous commonly used encryption systems. The NSA codebreakers have been able to decipher encryption from some virtual private networks, and this service was so popular that NSA was receiving 1,000 requests per hour from government clients. The NSA has also cracked the Secure Shell protocol, the Secure Socket Layer encryption method, and the Internet Protocol Security system.
Yet some encryption methods remain invulnerable to NSA decryption efforts. The e-mail service provider Zoho and the Tor network, also known as the Onion Router, have remained unbroken. The encryption programs Truecrypt and Off-the-Record have also continued to elude the decryption efforts of the NSA. The instant messaging system CSpace has thus far foiled solution, and ZRPT (a voice-over Internet protocol technology) has kept its secrets, too. ZRPT evolved from the Pretty Good Privacy program and evolved into GNU Privacy Guard.
Nick Note: We are as sure as we can be that Silent Circle encryption has not been compromised. Silent circle messages and phone call records have never been introduced in any criminal prosecutions. I was involved in the ZRPT (heart of silent circle) PGPFone and ZFhone development protocols.
ZRTP (composed of Z and Real-time Transport Protocol) 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 was developed by Phil Zimmermann, with help from Bryce Wilcox-O’Hearn, Colin Plumb, Jon Callas and Alan Johnston and was submitted to the Internet Engineering Task Force (IETF) by Zimmermann, Callas and Johnston on March 5, 2006 and published on April 11, 2011 as RFC 6189.[1]
I had access to the development software RFC 6189 . I had a few “friends” look over the source code. And we were certain their were no back doors. Link here: https://tools.ietf.org/html/rfc6189