RFC 5869 - HMAC-based Extract-and-Expand Key Derivation Function (HKDF)

RFC Number: 5869
Category: Informational
Published: May 2010
Authors: H. Krawczyk (IBM Research), P. Eronen (Nokia)

Contents

• 1. Introduction
• 2. HMAC-based Key Derivation Function (HKDF)
  • 2.1. Notation
  • 2.2. Step 1: Extract
  • 2.3. Step 2: Expand
• 3. Notes to HKDF Users
  • 3.1. To Salt or not to Salt
  • 3.2. The 'info' Input to HKDF
  • 3.3. To Skip or not to Skip
  • 3.4. The Role of Independence
• 4. Applications of HKDF
• 5. Security Considerations
• 6. Acknowledgments
• 7. References
  • 7.1. Normative References
  • 7.2. Informative References
• Appendix A. Test Vectors
  • A.1. Test Case 1
  • A.2. Test Case 2
  • A.3. Test Case 3
  • A.4. Test Case 4
  • A.5. Test Case 5
  • A.6. Test Case 6
  • A.7. Test Case 7
• Authors' Addresses

Abstract

This document specifies a simple Hashed Message Authentication Code (HMAC)-based key derivation function (HKDF), which can be used as a building block in various protocols and applications. The key derivation function (KDF) is intended to support a wide range of applications and requirements, and is conservative in its use of cryptographic hash functions.

Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc5869.

Copyright Notice

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