Framework Release 3.0 Background Since the release of the last edition of the NIST Smart Grid Framework and Roadmap for Interoperability Standards (Release 2.0), 1 in February 2012, significant technological advances in smart grid infrastructure have been implemented, supported by standards development across the entire smart grid arena. Examples include widespread deployment of wirelesscommunication power meters, availability of customer energy usage data through the Green Button initiative, remote sensing for determining real-time transmission and distribution status, and protocols for electric vehicle charging. The first release of the NIST Framework and Roadmap for Smart Grid Interoperability Standards (Release 1.0) 2 was published in January 2010. Release 3.0 updates NIST's ongoing efforts to facilitate and coordinate smart grid interoperability standards development and smart grid-related measurement science and technology, including the evolving and continuing NIST relationship with the Smart Grid Interoperability Panel (SGIP) public-private partnership. Over the last decade, Congress and the Administration have outlined a vision for the smart grid and have laid the policy foundation upon which it is being built. The Energy Independence and Security Act of 2007 (EISA) codified the policy of the United States to modernize the nation's electricity transmission and distribution system to create a smart electric grid. 3 The American Recovery and Reinvestment Act of 2009 (ARRA) accelerated the development of smart grid technologies, investing $4.5 billion for electricity delivery and energy reliability activities to modernize the electric grid and implement demonstration and deployment programs (as authorized under Title XIII of EISA). 4 5 The president, in his 2011 and 2012 State of the Union Addresses, reiterated his vision for a clean energy economy, 6 and he underscored the Administration's commitment in the "Blueprint for a Secure Energy Future." 7

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This publication has been developed by NIST in accordance with its statutory responsibilities under the Federal Information Security Modernization Act (FISMA) of 2014, 44 U.S.C. § 3551 et seq., Public Law (P.L.) 113-283. NIST is responsible for developing information security standards and guidelines, including minimum requirements for federal systems, but such standards and guidelines shall not apply to national security systems without the express approval of appropriate federal officials exercising policy authority over such systems. This guideline is consistent with the requirements of the Office of Management and Budget (OMB) Circular A-130. Nothing in this publication should be taken to contradict the standards and guidelines made mandatory and binding on federal agencies by the Secretary of Commerce under statutory authority. Nor should these guidelines be interpreted as altering or superseding the existing authorities of the Secretary of Commerce, Director of the OMB, or any other federal official. This publication may be used by nongovernmental organizations on a voluntary basis and is not subject to copyright in the United States. Attribution would, however, be appreciated by NIST.

This publication has been developed by NIST to further its statutory responsibilities under the Federal Information Security Modernization Act (FISMA), 44 U.S.C. § 3551 et seq., Public Law (P.L.) 113-283. NIST is responsible for developing information security standards and guidelines, including minimum requirements for federal information systems. Such information security standards and guidelines shall not apply to national security systems without the express approval of the appropriate federal officials exercising policy authority over such systems. This guideline is consistent with the requirements of the Office of Management and Budget (OMB) Circular A-130. Nothing in this publication should be taken to contradict the standards and guidelines made mandatory and binding on federal agencies by the Secretary of Commerce under statutory authority. Nor should these guidelines be interpreted as altering or superseding the existing authorities of the Secretary of Commerce, OMB Director, or any other federal official. This publication may be used by nongovernmental organizations on a voluntary basis, and is not subject to copyright in the United States. Attribution would, however, be appreciated by NIST.

Multicast authentication of synchrophasor data is challenging due to the design requirements of Smart Grid monitoring systems such as low security overhead, tolerance of lossy networks, time-criticality and high data rates. In this work, we propose inf -TESLA, Infinite Timed Efficient Stream Loss-tolerant Authentication, a multicast delayed authentication protocol for communication links used to stream synchrophasor data for wide area control of electric power networks. Our approach is based on the authentication protocol TESLA but is augmented to accommodate high frequency transmissions of unbounded length. inf TESLA protocol utilizes the Dual Offset Key Chains mechanism to reduce authentication delay and computational cost associated with key chain commitment. We provide a description of the mechanism using two different modes for disclosing keys and demonstrate its security against a man-in-the-middle attack attempt. We compare our approach against the TESLA protocol in a 2-day simulation scenario, showing a reduction of 15.82% and 47.29% in computational cost, sender and receiver respectively, and a cumulative reduction in the communication overhead.