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IETF RFC 3766
[ACTIVE]

Determining Strengths For Public Keys Used For Exchanging Symmetric Keys

Metadata

Publisher
IETF
Doc Type
Best Practice
Pages
23
Abstract
Implementors of systems that use public key cryptography to exchange symmetric keys need to make the public keys resistant to some predetermined level of attack. That level of attack resistance is the strength of the system, and the symmetric keys that are exchanged must be at least as strong as the system strength requirements. The three quantities, system strength, symmetric key strength, and public key strength, must be consistently matched for any network protocol usage. While it is fairly easy to express the system strength requirements in terms of a symmetric key length and to choose a cipher that has a key length equal to or exceeding that requirement, it is harder to choose a public key that has a cryptographic strength meeting a symmetric key strength requirement. This document explains how to determine the length of an asymmetric key as a function of a symmetric key strength requirement. Some rules of thumb for estimating equivalent resistance to large-scale attacks on various algorithms are given. The document also addresses how changing the sizes of the underlying large integers (moduli, group sizes, exponents, and so on) changes the time to use the algorithms for key exchange. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
Publication Date
2004-04-01
Status Note
Best Current Practice
DOI
10.17487/RFC3766
Link
https://doi.org/10.17487/RFC3766
Author(s)
Hilarie Orman
Paul E. Hoffman
Keyword(s)
Security, Cryptography
Latest version of IETF RFC 3766

Document Versions — IETF RFC 3766

  • ▶ IETF RFC 3766 (2004-04-01)
    THIS DOC [ACTIVE] [LATEST VERSION]

Bibliographic Reference(s)

  • ISBN.1565925203 — EFF EXTERNAL
  • Lenstra, A. K. and H. W. Lenstra, Jr. (eds), The development of the number field sieve, Lecture Notes in Math, 1554, Springer Verlag, Berlin, 1993. EXTERNAL
  • A. M. Odlyzko, Discrete logarithms: The past and the future, Designs, Codes, and Cryptography (1999). EXTERNAL
  • R. Schroeppel, et al., Fast Key Exchange With Elliptic Curve Systems, In Don Coppersmith, editor, Advances in Cryptology -- CRYPTO 31 August 1995. Springer-Verlag EXTERNAL
  • R. D. Silverman, "The Mythical MIPS Year", IEEE Computer, August 1999. EXTERNAL
  • RSA Labs Cryptobytes, Volume 1, No. 2 - Summer 1995; The Future of Integer Factorization, A. M. Odlyzko EXTERNAL
  • R. D. Silverman, RSA Laboratories Bulletin, Number 13 - April 2000, A Cost-Based Security Analysis of Symmetric and Asymmetric Key Lengths EXTERNAL
  • Shamir, Adi and Eran Tromer, "Factoring Large Numbers with the TWIRL Device", Advances in Cryptology - CRYPTO 2003, Springer, Lecture Notes in Computer Science 2729. EXTERNAL
  • J. Pollard, "Monte Carlo methods for index computation mod p", Mathematics of Computation, 32 (1978), 918-924. EXTERNAL
  • Gordon, D., "Discrete logarithms in GF(p) using the number field sieve", SIAM Journal on Discrete Mathematics, 6 (1993), 124-138. EXTERNAL
  • Dodson, B. and A. K. Lenstra, NFS with four large primes: an explosive experiment, Proceedings Crypto 95, Lecture Notes in Comput. Sci. 963, (1995) 372-385. EXTERNAL
  • Merkle, R.C., and Hellman, M., "On the Security of Multiple Encryption", Communications of the ACM, v. 24 n. 7, 1981, pp. 465-467. EXTERNAL
  • IETF RFC 1750 [Superseded*]
  • IETF RFC 2409 [Superseded*]
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IETF RFC 3766, Determining Strengths For Public Keys Used For Exchanging Symmetric Keys. Available at https://doi.org/10.17487/RFC3766
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IETF RFC 3766, Determining Strengths For Public Keys Used For Exchanging Symmetric Keys. Available at https://doi.org/10.17487/RFC3766

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IETF RFC 3766, Determining Strengths For Public Keys Used For Exchanging Symmetric Keys. Available at https://doi.org/10.17487/RFC3766
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<span class="citation"><cite>IETF RFC 3766</cite>, Determining Strengths For Public Keys Used For Exchanging Symmetric Keys. Available at <a href="https://doi.org/10.17487/RFC3766" target="_blank" rel="noopener">https://doi.org/10.17487/RFC3766</a></span>

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IETF RFC 3766, Determining Strengths For Public Keys Used For Exchanging Symmetric Keys
doi: 10.17487/RFC3766
url: https://doi.org/10.17487/RFC3766
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<cite id="bib-rfc3766">IETF RFC 3766</cite>, Determining Strengths For Public Keys Used For Exchanging Symmetric Keys
<span class="doi">10.17487/RFC3766</span>
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