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Versions: 00 01 02                                                      
INTERNET-DRAFT                                             J. M. Schanck
Intended Status: Experimental          Security Innovation & U. Waterloo
Expires: 2017-04-04                                             W. Whyte
                                                     Security Innovation
                                                                Z. Zhang
                                                     Security Innovation
                                                              2016-10-04


     Criteria for selection of public-key cryptographic algorithms
                  for quantum-safe hybrid cryptography
                   draft-whyte-select-pkc-qsh-02.txt


Abstract

   Authenticated key exchange mechanisms instantiated with cryptosystems
   based on integer factorization, finite field discrete log, or
   elliptic curve discrete log, are believed to be secure now but are
   vulnerable to a harvest-then-decrypt attack where an attacker who
   cannot currently break the mechanism records the traffic anyway, then
   decrypts it at some point in the future when quantum computers become
   available.  The Quantum-safe Hybrid approach is a modular design,
   allowing any authenticated key exchange mechanism to be protected
   against the harvest-then-decrypt attack by exchanging additional
   secret material protected with an ephemeral key for a quantum-safe
   public key cryptographic algorithm and including that secret material
   in the Key Derivation Function (KDF) run at the end of the key
   exchange.  This approach has been proposed in TLS as the Quantum-safe
   Hybrid handshake mechanism for Transport Layer Security protocol
   (QSH_TLS).  This document provides a guideline to criteria for
   selecting public key encryption algorithms approved for experimental
   use in the quantum safe hybrid setting.


Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html.




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   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   Update from last version: keeping alive till TLS WG review.







Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Quantum Attacks on Cryptosystems . . . . . . . . . . . . .  4
       2.1.1.  Shor's algorithm . . . . . . . . . . . . . . . . . . .  4
       2.1.2.  Grover's algorithm . . . . . . . . . . . . . . . . . .  5
     2.2.  Harvest-then-decrypt attack  . . . . . . . . . . . . . . .  5
     2.3.  Quantum-safe hybrid approach . . . . . . . . . . . . . . .  5
     2.4.  Symmetric algorithm  . . . . . . . . . . . . . . . . . . .  6
     2.5.  Random bit generation  . . . . . . . . . . . . . . . . . .  6
   3.  Selection Criteria . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Similar work . . . . . . . . . . . . . . . . . . . . . . .  6
     3.2.  Mandatory aspects  . . . . . . . . . . . . . . . . . . . .  7
       3.2.1.  Security levels  . . . . . . . . . . . . . . . . . . .  7
       3.2.2.  Freely available specifications of the algorithm . . .  7
       3.2.3.  Freely available source code for a reference
               implementation . . . . . . . . . . . . . . . . . . . .  8
     3.3 Desirable aspects  . . . . . . . . . . . . . . . . . . . . .  8
       3.3.1.  SUPERCOP implementation  . . . . . . . . . . . . . . .  8
       3.3.2.  Constant-time implementation . . . . . . . . . . . . .  9
       3.3.3.  Standardization  . . . . . . . . . . . . . . . . . . .  9
       3.3.4.  Patent and IP related issues . . . . . . . . . . . . .  9
   4.  Recommendations, justifications and considerations . . . . . .  9
     4.1.  Preliminary list of recommendations  . . . . . . . . . . .  9
     4.2.  Schemes under consideration  . . . . . . . . . . . . . . . 10
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
   Copyright Notice . . . . . . . . . . . . . . . . . . . . . . . . . 14



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1.  Introduction

   Quantum computers pose a significant threat to modern cryptography.
   The two most widely adopted public key cryptosystems, namely, RSA
   [PKCS1] and Elliptic Curve Cryptography (ECC) [SECG], will be broken
   by general purpose quantum computers.  RSA is adopted in TLS from
   Version 1.0 to TLS Version 1.3 [RFC2246], [RFC4346], [RFC5246],
   [TLS1.3].  ECC is enabled in RFC 4492 [RFC4492] and adopted in TLS
   version 1.2 [RFC5246] and 1.3 [TLS1.3].  Those two primitives are the
   only public key cryptography that TLS relies on.

   Although these algorithms are currently believed to be secure, data
   encrypted using these algorithms is vulnerable to a "harvest-then-
   decrypt" attack where an attacker who cannot currently break the
   mechanism records the traffic anyway, then decrypts it at some point
   in the future when quantum computers become available.  See section 2
   for a detailed account of those attacks.

   The Quantum-safe Hybrid approach, which has a concrete proposal as
   the Quantum-safe Hybrid handshake for Transport Layer Security
   protocol (QSH_TLS) [QSHTLS], addresses this attack by introducing a
   quantum-safe public key encapsulation mechanism along with the
   classical authenticated handshake.  QSH_TLS is a modular design that
   allows in principle for any quantum-safe encryption algorithm to be
   used in the hybrid approach.

   Since the IETF has not yet designated a single algorithm for use to
   provide quantum-safety, and since the quantum-safe algorithm used is
   intended to enhance security rather than being the only source of
   security, it is appropriate for there to be multiple algorithms that
   may be used in a quantum-safe hybrid setting.  This provides an
   opportunity for implementers to compare different quantum-safe
   algorithms before the choice of a single one becomes vital.  However,
   an algorithm should clearly satisfy some baseline set of criteria
   before it is approved for use in the quantum-safe hybrid setting,
   even if those criteria are more relaxed than they would be for
   selecting a single algorithm to rely on.

   This document specifies what those criteria are.

   The remainder of this document is organized as follows.  Section 2
   provides necessary background of the modular design of quantum-safe
   handshake for TLS.  Section 3 specifies selection criteria.  Section
   4 provides a preliminary list of recommended encryption algorithms.
   Section 5 describes IANA considerations.

   This is followed by the lists of normative and informative references
   cited in this document, the authors' contact information, and



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   statements on intellectual property rights and copyrights.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   Well-known abbreviations and acronyms can be found at RFC Editor
   Abbreviations List [REAL].

2.  Background

2.1.  Quantum Attacks on Cryptosystems

   If there exists a general purpose quantum computer, any cryptosystem
   that is built on top of the mathematical hard problems of integer
   factorization, finite field discrete logarithm (DL), or elliptic
   curve discrete logarithm (ECDL) will be vulnerable.  This includes
   RSA, DSA, DH, ECDH, ECDSA and other variants of these ciphers,
   including variants currently under consideration for standardization
   by CFRG and all public key cryptosystems used in TLS.  A quantum
   computer may allow a real-time attack on the authentication within a
   handshake protocol, or may allow an attacker to decrypt previously
   recorded network traffic.

   It is not clear when quantum computers will become available.  The EU
   has expressed in their Horizon 2020 project a desire for systems to
   be "quantum-ready" by 2020 [H2020].  Research groups have
   optimistically predicted practical and powerful quantum computer
   could become available by the same date [TPM15], which may be large
   enough to solve some instances of the elliptic curve discrete log
   problem that are currently secure.  It is, however, clear that data
   exchanged today may be vulnerable to the harvest-then-decrypt attack
   described below.

2.1.1.  Shor's algorithm

   Many of the hard problems used in public key cryptography can be
   reduced to the Hidden Subgroup Problem over a finite cyclic group.
   For an finite cyclic group G and finite set X, a function f : G -> X
   is said to hide a subgroup H if f(a) = f(b) iff a - b is in H.  The
   Hidden Subgroup Problem (HSP) is to determine the hidden subgroup H
   given black box access to f.  Shor's algorithm [SHOR97] is a
   probabilistic quantum algorithm that solves the HSP over any finite
   cyclic group in polynomial time.  Among the problems that reduce to
   the HSP are the integer factorization and discrete logarithm problems
   that underly RSA, DSA, DH, ECDH, and ECDSA, hence all of these
   systems are vulnerable to quantum attacks.




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2.1.2.  Grover's algorithm

   Grover's algorithm [GROV96] is a probabilistic quantum algorithm that
   finds the unique input to a black box function that produces a
   particular output value.  Compared with classical algorithms,
   Grover's algorithm finds the solution with a quadratic boost, i.e.,
   within O(N^(1/2)) evaluations of the function, where N is the size of
   the function's domain.

   While an exact cost analysis of Grover's algorithm will depend
   crucially on architecture dependent parameters that are not currently
   available, it is a common belief among cryptographers that Grover's
   algorithm is effective against symmetric primitives [BRA98].  To be
   conservative we ignore constant factors and simply assume that
   Grover's algorithm finds preimages quadratically faster than
   classical brute force search.  Likewise, we assume that Grover's
   algorithm reduces the time required to recover the key of a symmetric
   cipher by a quadratic factor.  As an example, AES-256 provides 256
   bits of security against classical computers, but is assumed to
   provide only 128 bits of security against quantum computers.

2.2.  Harvest-then-decrypt attack

   The harvest-then-decrypt attack is a straightforward yet effective
   attack.  In such an attack, the attacker stores encrypted data for
   long periods of time until legal, technological, or cryptanalytic
   means become available for revealing keys.

   Under the context of quantum computing, this attack becomes extremely
   powerful.  TLS relies on RSA and ECC, both will be broken when
   quantum computer becomes available.  Hence, any data encrypted now
   will be vulnerable to this attack.  It is likely that it will be some
   time before breaks become so cheap that all harvested traffic can be
   decrypted.  However, this is little consolation to the people whose
   traffic is initially targeted for decryption.  It seems prudent to
   provide protection against the harvest-then-decrypt attack natively
   to secure data exchange protocols as soon as possible.

2.3.  Quantum-safe hybrid approach

   The quantum safe hybrid approach defeats the quantum harvest-then-
   decrypt attack by introducing a second quantum-safe cryptographic
   primitive running in parallel with existing handshake approaches.
   This measure assures that when the classical cryptography fails, the
   attacker still need to break the corresponding quantum-safe
   encryption algorithm.

   It is easy to see that this approach is at least as strong as the



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   stronger primitive of classical cryptography and the quantum-safe
   cryptography in the pre-quantum world [QSHTOR]. Therefore, it is an
   ideal approach to migrate into quantum-safe cryptography for TLS as
   it does not reduce the security guarantees that TLS is already
   delivering; in the meantime, it allows for trial usage of quantum-
   safe algorithms and protects data against the aforementioned harvest-
   the-decrypt attack.

2.4.  Symmetric algorithm

   For 128 bit security, implementations of a quantum-safe hybrid
   approach SHOULD use a symmetric algorithm with a 256-bit key, but MAY
   use a symmetric algorithm with a 128-bit key for interoperability or
   performance reasons.

2.5.  Random bit generation

   For 128 bit security, implementations of a quantum-safe hybrid
   approach SHOULD ensure that any Deterministic Random Bit Generator
   (DRBG) used in key generation or encryption for a quantum-safe
   primitives is instantiated with at least 256 bits of entropy from a
   secure random source.

3.  Selection Criteria

   The hybrid approach is a modular design, which, in order to support
   various quantum-safe algorithms, does not recommend any specific
   quantum-safe encryption algorithm.  In this section we give
   guidelines for selecting encryption algorithms that are suitable for
   experimental use in the hybrid approach.

3.1.  Similar work

   To date, multiple groups have been involved in the work of evaluating
   quantum-safe encryption algorithms.

      o   The National Security Agency of the United States has
      announced a plan to migrate to quantum-safe cryptography [NSA15].

      o   The ETSI Quantum-Safe Cryptography (QSC) Industry
      Specification Group (ISG) aims to assess and make recommendations
      for quantum-safe cryptographic primitives and protocols, taking
      into consideration both the current state of academic cryptology
      and quantum algorithm research, as well as industrial requirements
      for real-world deployment [ETSIQ].

      o   The Secure Architectures of Future Emerging Cryptography
      (SAFEcrypto) project [SAFEC], supported by H2020 project, focuses



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      on practical implementation of quantum-safe encryptions
      algorithms, particularly lattice-based public key cryptography.

      o   The Post-quantum cryptography for long-term security
      (PQCRYPTO) group, also supported by H2020 project, has made their
      initial recommendations of long-term secure post-quantum systems
      [PQCRY].

   Note that PQCRYPTO is the only group that has made initial
   recommendations on quantum-safe cryptography.

   This document describes criteria for quantum-safe encryption
   algorithms, with a focus on those algorithms existing today and
   suitable for transitional use until the quantum era.  The intent is
   ultimately to align with other industry groups while enabling earlier
   deployment of algorithms that can reasonably be expected to make
   things better, not worse.


3.2.  Mandatory aspects

   Algorithms to be considered by quantum-safe hybrid approach MUST meet
   the following criteria.

3.2.1.  Security levels

   The candidate algorithm MUST provide 128 bit security in the quantum-
   safe setting.

   If the candidate algorithm is subject to decryption failures, these
   MUST happen with a probability of less than 2^-74 (such that 128
   billion devices (2^7 * 2^30) each initiating 128 billion connections
   (2^7 * 2^30) will with high probability encounter no decryption
   failures).  Note that an attacker will be able to create invalid
   messages that do not decrypt correctly, so an implementation will
   have to correctly handle this failure case even when the chance of a
   decryption failure is negligible on a valid message (or even when
   this chance is zero).


3.2.2.  Freely available specifications of the algorithm

   The candidate algorithm MUST have a set of publicly accessible
   documents specifying common techniques and implementation choices.
   The documents MAY be Internet Drafts.  Topics MUST include:

      o   Cryptographic primitives: the building blocks for a secure
      cryptographic scheme;



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      o   Cryptographic schemes: complete sequences of operations for
      performing secure cryptographic functions;

      o   Supported parameter choices: specific selections of approved
      sets of values for cryptographic parameters;

      o   Classical security levels for the proposed parameter sets;

      o   Argument for post-quantum security levels for the proposed
      parameter sets;

      o   Encoding of cryptographic data items: specifies
      encoding/decoding of public keys and ciphertexts.

   In addition, it MAY include relevant information to assist in the
   development and interoperable implementation, including:

      o   Security considerations;

      o   Open issues.

3.2.3.  Freely available source code for a reference implementation

   It is important to have a stable reference implementation available
   for the candidate algorithm.  The code needs to be rigorously tested
   and reviewable.  A poor implementation of a good cryptosystem can be
   as harmful as a broken cryptosystem.

   The implementation SHOULD also be open source to allow for public
   auditing.  In particular, any default choice of parameters MUST be
   justified.

3.3 Desirable aspects

   The following aspects are desirable.  Algorithms that meet those
   criteria are preferred.

3.3.1.  SUPERCOP implementation

   System for Unified Performance Evaluation Related to Cryptographic
   Operations and Primitives (SUPERCOP) [SUPEC] is a toolkit developed
   by the Virtual Application and Implementation Research (VAMPIRE) Lab
   for measuring the performance of cryptographic software.  The latest
   release of SUPERCOP measures the performance of hash functions,
   secret key stream ciphers, public key encryption systems, public key
   signature systems, and public key secret sharing systems.

   The candidate algorithm MAY have a reference implementation for



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   SUPERCOP.  Performance of the implementation on SUPERCOP MAY be taken
   into consideration when selections are made.

3.3.2.  Constant-time implementation

   An implementation of a cryptosystem is constant-time means that the
   time for encryption/decryption functions is constant, regardless of
   the input and the output of the functions.  As an example, the time
   to decrypt any valid ciphertext should use a same time as decrypting
   an invalid ciphertext and producing a decryption error.  Constant
   time implementation is important for cryptography as it makes side-
   channel attacks substantially harder.

   Algorithms with provable constant time implementations SHOULD be
   preferred. However, this is not an absolute requirement as the QSH
   setting uses ephemeral keys and an implementation of QSH SHOULD only
   decrypt once with any key, so an attacker is unlikely to gain
   sufficient information from the time of a single decryption to
   recover the plaintext.

3.3.3.  Standardization

   The candidate algorithm MAY be standardized by another standards
   body, such as ANSI X.9, IEEE, or ETSI.  Algorithms that maintain
   creditability among multiple standards bodies SHOULD be preferred.

3.3.4.  Patent and IP related issues

   The candidate algorithm MAY be either non-patented or patented but
   with FRAND (Free or Reasonable and Non-Discriminatory) licensing
   statement made and all relevant IETF IP declarations provided.

4.  Recommendations, justifications and considerations

4.1.  Preliminary list of recommendations

   The following list is an (incomplete) list of recommended quantum-
   safe encryption algorithms and parameters for 128 bits security that
   MAY be considered in the hybrid approach.

      o   NTRUEncrypt lattice-based encryption scheme with parameter
      sets ees443ep1, ees587ep1, and ees743ep1 as defined in [EESS1];

         o   Specification: [EESS1] provides a concrete specification of
         NTRUEncrypt with parameter set ees443ep1, ees587ep1, and
         ees743ep1, including primitives, syntax, reference to classical
         security analysis in [HOF15], quantum security analysis, and
         encode/decode mechanisms



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         o   Open-sourced reference implementation: Available from
         [NTRU-GIT]

         o   SUPERCOP implementation: Available for related parameter
         sets, not yet available for the recommended parameter sets

         o   Constant-time implementation: Not yet available

         o   Standardization: The recommended parameter sets have not
         been published in a standard, but the encryption scheme and
         other parameter sets have been standardized in IEEE 1363.1 and
         ANSI X9.98.

         o   Patent and IP Issues: NTRUEncrypt is subject to patents
         held by Security Innovation. Security Innovation has provided
         IPR Declaration 2588 to IETF.

4.2.  Schemes under consideration

   The following schemes are under consideration. They are well known
   quantum safe encryption algorithms in the literature.  However, due
   to the lack of specifications, implementation of those schemes are
   non-trivial.  For this reason we list those schemes as "under
   consideration".  They will be promoted to the recommendation list
   once detailed specifications are provided.

      o   Learning with error lattice-based encryption scheme [REG05],
      with parameter set form [LIN11];

      o   NTRUEncrypt lattice-based encryption scheme instantiated with
      learning with error problem [STE11];

      o   McEliece code-based encryption scheme [MCELI] with parameter
      set for McBits [MCBIT];

      o   McEliece code-based encryption scheme with Quasi-cyclic
      Moderate Density Parity-Check (MDPC) codes [MDPC].

5.  IANA Considerations

   This document does not establish any new IANA registries, nor does it
   add any entries to existing registries.

6.  References

6.1.  Normative References





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   [BER09]    Bernstein, D., "Cost analysis of hash collisions: Will
              quantum computers make SHARCS obsolete?", SHARCS'09.
              <http://cr.yp.to/hash/collisioncost-20090823.pdf>

   [BRA98]    Brassard, G., Hoyer, P., and Tapp, A., "Quantum
              cryptanalysis of hash and claw-free functions", LATIN'98:
              Theoretical Informatics.

   [EESS1]    Consortium for Efficient Embedded Security, "Efficient
              Embedded Security Standard #1: Implementation Aspects of
              NTRUEncrypt", March 2015.
              <https://github.com/NTRUOpenSourceProject/ntru-
              crypto/raw/master/doc/EESS1-2015v3.0.pdf>

   [ETSIQ]    ETSI White Paper No. 8, "Quantum Safe Cryptography and
              Security: An introduction, benefits, enablers and
              challenges", June 2015.

   [GROV96]   Grover, L., "A fast quantum mechanical algorithm for
              database search", STOC 1996.

   [H2020]    Lange, T., "PQCRYPTO project in the EU", April, 2015.
              <http://pqcrypto.eu.org/slides/20150403.pdf>

   [HOF15]    Hoffstein, J., Pipher, J., Schanck, J., Silverman, J.,
              Whyte, W., and Zhang, Z., "Choosing Parameters for
              NTRUEncrypt", 2015. <https://eprint.iacr.org/2015/708>

   [LIN11]    Lindner, R., and Peikert, C., "Better Key Sizes (and
              Attacks) for LWE-Based Encryption", 2011.

   [MCBIT]    Bernstein, D., Chou, T., and Schwabe, P., "McBits: Fast
              Constant-Time Code- Based Cryptography", 2013.

   [MCELI]    McEliece, R., "A Public-Key Cryptosystem Based On
              Algebraic Coding Theory", 1978.

   [MDPC]     Misoczki, R., Tillich, J., Sendrier, N., and Barreto, P.,
              "MDPC-McEliece: New McEliece variants from Moderate
              Density Parity-Check codes", 2013.

   [NSA15]    NSA, "NSA Suite B Cryptography", Aug 19, 2015.
              <https://www.nsa.gov/ia/programs/suiteb_cryptography/>

   [NTRU-GIT] https://github.com/NTRUOpenSourceProject/NTRUEncrypt

   [PKCS1]    RSA Laboratories, "PKCS#1: RSA Encryption Standard version
              1.5", PKCS 1, November 1993



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   [PQCRY]    PQCRYPTO, "Initial recommendations of long-term secure
              post-quantum systems".
              <http://pqcrypto.eu.org/docs/initial-recommendations.pdf>

   [QSHTLS]   Schanck, J., Whyte, W., and Zhang, Z., "Quantum-Safe
              Hybrid (QSH) Ciphersuite for Transport Layer Security
              (TLS) version 1.3", draft-whyte-qsh-tls13-00, July 2015.

   [QSHTOR]   Schanck, J., Whyte, W., and Zhang, Z., "A quantum-safe
              circuit-extension handshake for Tor", March 2015.
              <https://eprint.iacr.org/2015/287>

   [REAL]     "RFC Editor Abbreviations List", September 2013,
              <https://www.rfc-editor.org/rfc-style-
              guide/abbrev.expansion.txt/>.

   [REG05]    Regev, O., "On lattices, learning with errors, random
              linear codes, and cryptography", 2005.


   [RFC2119]  Bradner, S., "Key Words for Use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, January 1999.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 2434, October
              1998.

   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346, April 2006.

   [RFC4492]  Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
              Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
              for Transport Layer Security (TLS)", RFC 4492, May 2006.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [SAFEC]    Secure Architectures of Future Emerging Cryptography
              (SAFEcrypto). <http://www.safecrypto.eu/>

   [SHOR97]   Shor, P., "Polynomial-time algorithms for prime
              factorization and discrete logarithm problems", SIAM J.
              Computing 26 (1997), 1484-1509.
              <http://www.research.att.com/~shor/papers/QCjournal.pdf>




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   [STE11]    Stehle, D., and Steinfield, R., "Making NTRUEncrypt and
              NTRUSign as secure as worst-case problems over ideal
              lattices", 2011.

   [TLS1.3]   Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", draft-ietf-tls-tls13-05, March 2015.

   [TPM15]    Morgan, T., "Google Sees Long, Expensive Road Ahead For
              Quantum Computing", July 2015.
              <http://www.theplatform.net/2015/07/22/google-sees-long-
              expensive-road-ahead-for-quantum-computing/>


6.2.  Informative References



   [RFC4366]  Blake-Wilson, S., Nysrom, M., Hopwood, D., Mikkelsen, J.,
              and T. Wright, "Transport Layer Security (TLS)
              Extensions", RFC 4366, April 2006.

   [RFC5990]  Randall, J., Kaliski, B., Brainard, J. and Turner S., "Use
              of the RSA-KEM Key Transport Algorithm in the
              Cryptographic Message Syntax (CMS)", RFC 5990, September
              2010.

   [RFC5859]  Krawczyk, H., Eronen, P., "HMAC-based Extract-and-Expand
              Key Derivation Function (HKDF)", RFC 5859, May 2010.



Authors' Addresses

   John M. Schanck
   Security Innovation, US
   and
   University of Waterloo, Canada
   jschanck@securityinnovation.com


   William Whyte
   Security Innovation, US
   wwhyte@securityinnovation.com


   Zhenfei Zhang
   Security Innovation, US
   zzhang@securityinnovation.com



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INTERNET DRAFT     PKC Selecting Criteria for QSH-TLS         2016-10-04


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