Bullrun (decryption program)

According to the Bullrun classification guide published by The Guardian, the program uses multiple methods including computer network exploitation,[3] interdiction, industry relationships, collaboration with other intelligence community entities, and advanced mathematical techniques.

[1] A number of technical details regarding the program found in Snowden's documents were additionally censored by the press at the behest of US intelligence officials.

[1][2] Access to the program is limited to a group of top personnel at the Five Eyes (FVEY), the NSA and the signals intelligence agencies of the United Kingdom (GCHQ), Canada (CSE), Australia (ASD), and New Zealand (GCSB).

[2] Through the NSA-designed Clipper chip, which used the Skipjack cipher with an intentional backdoor, and using various specifically designed laws such as CALEA, CESA and restrictions on export of encryption software as evidenced by Bernstein v. United States, the U.S. government had publicly attempted in the 1990s to ensure its access to communications and ability to decrypt.

[5] According to a Bullrun briefing document, the agency had successfully infiltrated both the Secure Sockets Layer as well as some virtual private networks (VPNs).

'"[5] Several experts, including Bruce Schneier and Christopher Soghoian, had speculated that a successful attack against RC4, an encryption algorithm used in at least 50 percent of all SSL/TLS traffic at the time, was a plausible avenue, given several publicly known weaknesses of RC4.

In the wake of Bullrun revelations, some open source projects, including FreeBSD and OpenSSL, have seen an increase in their reluctance to (fully) trust hardware-based cryptographic primitives.

[21] There has been speculation that the NSA was aware of the Heartbleed bug, which caused major websites to be vulnerable to password theft, but did not reveal this information in order to exploit it themselves.