Data Security holds on efficient basis conversion. It expired in 2017. Hewlett-Packard holds on compression and decompression of data points on elliptic curves. It expired in 2018. According to the NSA, Certicom holds over 130 patents relating to elliptic curves and public key cryptography in general. It is difficult to create a complete list of patents that are related to ECC, but a good starting point is the Standards for Efficient Cryptography Group (SECG) – a group devoted exclusively to developing standards based on ECC, however, https://www.secg.org/ the group's official website has an indicator that states "shut down for repairs" since 2014, and it states that "The site is being restored" since then. There is controversy over the validity of some of the patent claims. Certicom's lawsuit against Sony On May 30, 2007, Certicom filed a lawsuit against Sony in United States District Court for the Eastern District of Texas Marshall office, claiming that Sony's use of ECC in Advanced Access Content System and Digital Transmission Content Protection violates Certicom's patents for that cryptographic method. In particular, Certicom alleged violation of and . The lawsuit was dismissed on May 27, 2009. The stipulation states, "Whereas Certicom and Sony have entered into a settlement agreement pursuant to which they have agreed to a dismissal without prejudice, these parties therefore jointly move to dismiss all claims and counterclaims asserted in this suit, without prejudice to the right to pursue any such claims and counterclaims in the future." As for the prior art, Sony claimed: For '870 patent: Alfred J. Menezes, Minghua Qu and Scott A. Vanstone, IEEE P1363 Standard, Standard for RSA, Diffie–Hellman and Related Public-Key Cryptography, Part 6: Elliptic Curve Systems (Draft 2) (October 30, 1994) For '928 patent: Scott A. Vanstone, G. B. Agnew and R. C. Mullin, An implementation of elliptic curve cryptosystems over F2155, IEEE Journal on Selected Areas in Communications, Volume 11, Issue 5, Jun 1993 p. 804 - 813 See also Elliptic curve cryptography References External links Harper, Menezes and Vanstone, Public-Key Cryptosystems with Very Small Key Lengths, EUROCRYPT '92 (LNCS 658) Elliptic curve cryptography Cryptography law Software patent law