Archived NIST Technical Series Publication The attached publication has been archived (withdrawn), and is provided solely for historical purposes. It may have been superseded by another publication (indicated below). Archived Publication Series/Number: NIST Special Publication 800-177 Title: Trustworthy Email Publication Date(s): September 2016 Withdrawal Date: February 26, 2019 Withdrawal Note: This publication has been superseded in its entirety by SP 800-177 Revision 1. Superseding Publication(s) The attached publication has been superseded by the following publication(s): Series/Number: NIST Special Publication 800-177 Revision 1 Title: Trustworthy Email Author(s): Scott Rose; J. Stephen Nightingale; Simson L. Garfinkel; Ramaswamy Chandramouli Publication Date(s): February 2019 URL/DOI: https://doi.org/10.6028/NIST.SP.800-177r1 Additional Information (if applicable) Contact: Advanced Network Technology Division (Information Technology Laboratory) Latest revision of the attached publication: Related information: https://www.nist.gov/programs-projects/high-assurance-domains https://csrc.nist.gov/publications/detail/sp/800-177/archive/2016-09-07 Withdrawal N/A announcement (link): Date updated: February 26, 2019 NIST Special Publication 800-177 Trustworthy Email Ramaswamy Chandramouli Simson Garfinkel Stephen Nightingale Scott Rose This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-177 C O M P U T E R S E C U R I T Y NIST Special Publication 800-177 Trustworthy Email Scott Rose, Stephen Nightingale Information Technology Laboratory Advanced Network Technology Division Simson L. Garfinkel Information Technology Laboratory Information Access Division Ramaswamy Chandramouli Information Technology Laboratory Computer Security Division This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-177 September 2016 U.S. Department of Commerce Penny Pritzker, Secretary National Institute of Standards and Technology Willie May, Under Secretary of Commerce for Standards and Technology and Director Authority 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. § 3541 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, 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, Section 8b(3), Securing Agency Information Systems, as analyzed in Circular A-130, Appendix IV: Analysis of Key Sections. Supplemental information is provided in Circular A-130, Appendix III, Security of Federal Automated Information Resources. 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. National Institute of Standards and Technology Special Publication 800-177 Natl. Inst. Stand. Technol. Spec. Publ. 800-177, 84 pages (Sept. 2016) CODEN: NSPUE2 This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-177 Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by NIST, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. There may be references in this publication to other publications currently under development by NIST in accordance with its assigned statutory responsibilities. The information in this publication, including concepts and methodologies, may be used by federal agencies even before the completion of such companion publications. Thus, until each publication is completed, current requirements, guidelines, and procedures, where they exist, remain operative. For planning and transition purposes, federal agencies may wish to closely follow the development of these new publications by NIST. Organizations are encouraged to review all draft publications during public comment periods and provide feedback to NIST. All NIST Computer Security Division publications, other than the ones noted above, are available at http://csrc.nist.gov/publications. National Institute of Standards and Technology Attn: Advanced network Technologies Division, Information Technology Laboratory 100 Bureau Drive (Mail Stop 8920) Gaithersburg, MD 20899-8920 Email: [email protected] ii ______________________________________________________________________________________________________ Reports on Computer Systems Technology The Information Technology Laboratory (ITL) at the National Institute of Standards and Technology (NIST) promotes the U.S. economy and public welfare by providing technical leadership for the Nation’s measurement and standards infrastructure. ITL develops tests, test methods, reference data, proof of concept implementations, and technical analyses to advance This the development and productive use of information technology. ITL’s responsibilities include the publication development of management, administrative, technical, and physical standards and guidelines for the cost-effective security and privacy of other than national security-related information in federal information systems. The Special Publication 800-series reports on ITL’s research, guidelines, and outreach efforts in information system security, and its collaborative activities with industry, government, and academic organizations. is available Abstract This document gives recommendations and guidelines for enhancing trust in email. The primary audience includes enterprise email administrators, information security specialists and network free managers. This guideline applies to federal IT systems and will also be useful for small or of medium sized organizations. Technologies recommended in support of core Simple Mail charge Transfer Protocol (SMTP) and the Domain Name System (DNS) include mechanisms for authenticating a sending domain: Sender Policy Framework (SPF), Domain Keys Identified Mail (DKIM) and Domain based Message Authentication, Reporting and Conformance (DMARC). from: Recommendations for email transmission security include Transport Layer Security (TLS) and associated certificate authentication protocols. Recommendations for email content security include the encryption and authentication of message content using S/MIME http://dx.doi.org/10.6028/NIST.SP.800-177 (Secure/Multipurpose Internet Mail Extensions) and associated certificate and key distribution protocols. Keywords Email; Simple Mail Transfer Protocol (SMTP); Transport Layer Security (TLS); Sender Policy Framework (SPF); Domain Keys Identified Mail (DKIM); Domain based Message Authentication, Reporting and Conformance (DMARC); Domain Name System (DNS) Authentication of Named Entities (DANE); S/MIME; OpenPGP. iii ______________________________________________________________________________________________________ Acknowledgements Audience This document gives recommendations and guidelines for enhancing trust in email. The primary audience for these recommendations is enterprise email administrators, information security This specialists and network managers. While some of the guidelines in this document pertain to federal IT systems and network policy, most of the document will be more general in nature and publication could apply to any organization. For most of this document, it will be assumed that the organization has some or all responsibility for email and can configure or manage its own email and Domain Name System (DNS) systems. is Even if this is not the case, the guidelines and recommendations in this document may help in available education about email security and can be used to produce a set of requirements for a contracted service. Trademark Information free All registered trademarks belong to their respective organizations. of charge from: http://dx.doi.org/10.6028/NIST.SP.800-177 iv NIST SP 800-177 Trustworthy Email ______________________________________________________________________________________________________ Executive Summary This document gives recommendations and guidelines for enhancing trust in email. The primary audience includes enterprise email administrators, information security specialists and network managers. This guideline applies to federal IT systems and will also be useful for small or This medium sized organizations. publication Email is a core application of computer networking and has been such since the early days of Internet development. In those early days, networking was a collegial, research-oriented enterprise. Security was not a consideration. The past forty years have seen diversity in applications deployed on the Internet, and worldwide adoption