Patent-related uncertainty around elliptic curve cryptography (ECC), or ECC patents, is one of the main factors limiting its wide acceptance. For example, the OpenSSL team accepted an ECC patch only in 2005 (in OpenSSL version 0.9.8), despite the fact that it was submitted in 2002. According to Bruce Schneier as of May 31, 2007, "Certicom certainly can claim ownership of ECC. The algorithm was developed and patented by the company's founders, and the patents are well written and strong. I don't like it, but they can claim ownership." Additionally, NSA has licensed MQV and other ECC patents from Certicom in a US$25 million deal for NSA Suite B algorithms. (ECMQV is no longer part of Suite B.) However, according to RSA Laboratories, "in all of these cases, it is the implementation technique that is patented, not the prime or representation, and there are alternative, compatible implementation techniques that are not covered by the patents." Additionally, Daniel J. Bernstein has stated that he is "not aware of" patents that cover the Curve25519 elliptic curve Diffie–Hellman algorithm or its implementation. , published in February 2011, documents ECC techniques, some of which were published so long ago that even if they were patented any such patents for these previously published techniques would now be expired. Known patents Certicom holds a patent on efficient GF(2n) multiplication in normal basis representation; expired in 2016. Certicom holds multiple patents which cover the MQV (Menezes, Qu, and Vanstone) key agreement technique: expired in 2015 expired in 2015 expired in 2015 expired in 2015 expired in 2017 /EP0739105B1 expired in 2016 Certicom holds on the technique of validating the key exchange messages using ECC to prevent a man-in-the-middle attack, which expired in 2016. Related , , also expired in 2016 and expired in 2018. Certicom holds and regarding digital signatures on a smartcard; these expired in 2017 and 2016 respectively. Certicom holds on calculating the x-coordinate of the double of a point in binary curves via a Montgomery ladder in projective coordinates. The priority date is Jan 29, 1997, and the filing date is Oct 2, 2000. Claims disclosed in the original patent application have expired but some claims may still be enforceable until 2020. US National Security Agency holds , , , on efficient GF(2n) calculations on a normal basis (all of these patents expired or lapsed (as Google shows) due to failure to pay fees) RSA