Privacy-enhancing cryptography at NIST...Apr 11, 2019 · 1.Crypto Standards at NIST Several...

Privacy-enhancing cryptography at NIST

Lúıs Brandão and René Peralta 1

1National Institute of Standards and Technology (Gaithersburg MD, USA)

Presented at the 2nd ZKProof WorkshopApril 11, 2019 (Berkeley, USA)

Contact email: [email protected]

1/21

Outline

1. Crypto Standards at NIST

2. Privacy-Enhancing Crypto

3. Our perspective on ZKProof

4. Conclusions

2/21


Outline




4. Conclusions

3/21


Some history

I 1977: FIPS 46 ”Data Encryption Standard (DES)”

I 1990s: Public–key Cryptography (FIPS 186, SP 800-56A/56B)

I 2001: FIPS 197 “Advanced Encryption Standard (AES)”

I Dual EC DRBG episode

I 2015: FIPS 202 “SHA-3” (Secure Hash Function 3)

I Ongoing standardization projectsI Post-Quantum Cryptography (PQC)I Lightweight Cryptography (LWC)I Threshold Cryptography

4/21


Several approaches

I Cryptographic algorithm competitions.I Advanced Encryption Standard (AES).I Secure Hash Algorithm – 3 (SHA-3).

I Adopt standards from other standardization organizations.I Develop new standards.

I In-house development based on well-accepted research results(e.g. SP 800-56C).

I Selected among submissions (e.g. modes of operations in SP800-38 series).

I Not a competition, but based on call for submissions.I PQC, LWC.

I Open to other approaches...

5/21


Overview of NIST Crypto Standards

6/21


Privacy at NIST

NIST Privacy Frameworkhttps://www.nist.gov/privacy-framework

I Envisioned to be a voluntary enterprise riskmanagement tool to help organizationsmanage individuals’s privacy risk

I Drafting the NIST Privacy Framework:Workshop #2 in Atlanta, May 13–14

Data de-identification challengese.g. https://www.herox.com/UnlinkableDataChallenge/community

Privacy-enhancing Cryptography. This presentation.

7/21

https://www.nist.gov/privacy-frameworkhttps://www.nist.gov/news-events/events/2019/05/drafting-nist-privacy-framework-workshop-2https://www.herox.com/UnlinkableDataChallenge/community


Outline




4. Conclusions

8/21


The NIST PEC project

Privacy-Enhancing Cryptography (PEC):https://csrc.nist.gov/Projects/Privacy-Enhancing-Cryptography

I It’s been dormant ... now getting revived.

I Fundamental role for SMPC and zero-knowledge proofs.

I An important goal: develop useful reference materials.

9/21

https://csrc.nist.gov/Projects/Privacy-Enhancing-Cryptography


Reference materials

In order to

I Assess the state of things in a particular area.

I Motivate real-use applications or proofs of concept.

I Frame development of standards and future discussions.

I Enable interoperability for companies doing things now.

Context is PEC use-cases:

I Brokered identification

I “Students’ right to know”

I Privacy-preserving public auditability

10/21


Use-case: Brokered identification in FCCX (1/2)

Manage protocol

Hub

IDP SP

User

I Why this example? It relates to privacy; relates to the identityframework use-case in the ZKProof docs.

I Design constraints in place: mostly-passive user; broker mustexist. (We can’t always chose the optimal solution paradigm)

I Not enough privacy-preserving reference material forengineers.

11/21


Use-case: Brokered identification in FCCX (2/2)

4. Signllub(request)

Hub

6. SignID� atts)

User (assertion)

User

2. SignSP(request)

9. SignHub

�atts)

(assertion)

SP

User

5. Authenticate to Ifil 3. Select Ifil 1. Request resource-----------------------------------------------------------------------------------------------------------

vvv, (redirection I u -=I= vi (user-pseudonym, via user-agent) persistent and anonymous)

atts == {name == John Doe, address == Street X, Bday_ == ''1/2/1993'', �

The “National Strategy for Trusted Identities in Cyberspace” wantedprivacy properties for this, e.g.:

I End-to-end encrypted attributes

I Unlinkability of user-transactions by the Hub

PEC can solve it ... but even a simple (semi-honest) Diffie-HellmanKey-Exchange was beyond vendors’ capabilities.

12/21


Use-case: Student’s right to know

I Proposal to mandate the use of SMPC to calculate themonetary return on student’s investment on education.

I Data is distributed among several entities. Because of privacyconcerns, these entities cannot share the data.

I https://www.govtrack.us/congress/bills/116/s681/text

13/21

https://www.govtrack.us/congress/bills/116/s681/text


Use-case: public-auditability with randomness

The NIST Randomness Beacon

I Broadcasts a randomness pulse every 60 seconds

I Each pulse commits to a fresh 512-bit random string

I Each pulse is time-stamped and signed by NIST

I Hash-chained pulses for an immutable public record

I Cryptographic fields support strong trust assurance

1 1 0

1 1

1 0

1 0 1

1 0

0 0

1 0

0 0 1

1 1

1 1

0 0

1 1

0

1 1 1

0 0

1 0

0 0

1

1 01

1 0

1 0

0 0

0 1

1 0 0

1

1 1 0

0 1

0 0

0 0

1 0

0 1

0 0

0 1

0 1

0 1

1 1

1 1

0 1

1 0

1 1

0 1

1 1 1

0 0 1

1 0

1 0

1 0

1 0

0 1

1 1

HSM

Clock

RNG

RNG#3

Beacon Engine

Time server

Pulse

RNG Sign

externalentropy

BeaconApp

Firew

all

Public randomness facilitates public auditability of randomized processes.

Enhancing them with privacy-preserving properties is a matter of PEC.

14/21

https://beacon.nist.gov/home


Research in multiplicative complexity (MC)

I Reference circuits for AES

I MC is relevant for ZK, SMPC, ..., since usually XOR gates arefree and ANDs are expensive

I Intention to develop a circuit file format

15/21


Outline




4. Conclusions

16/21


ZKProof assessment

Our perspective of the ZKProof initiative:

I ZKProof is well within the reference materials approach

I Documentation can evolve to a useful reference

I Recent engagement: LaTeX porting, propose developing areference, sent comments

17/21


ZKProof assessment

Do conceivable use-cases fit within the process being developed?

I Good scenario: spend time building things, and they turn outto be useful in achieving myriad functionalities.

I Bad scenario: spend 10 years on something and not enablesomething we now know is important.

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4. Conclusions

Outline




4. Conclusions

19/21

4. Conclusions

Final Remarks

I NIST is interested in crypto development and interoperability

I That is achieved via standards and reference material

I NIST PEC wants to keep up to date with, and support,external initiatives

I NIST PEC is interested in supporting ZKProof

20/21

4. Conclusions

Thank you for your attention

The PEC team is

I Lúıs Brandão

I René Peralta

I Angela Robinson

email : [email protected]

21/21

Privacy-enhancing cryptography at NISTCoverOutline

1 Crypto Standards at NISTOutlineSome historySeveral approachesOverview of NIST Crypto StandardsPrivacy at NIST

2 Privacy-Enhancing CryptoOutlineThe NIST PEC projectReference materialsUse-case: Brokered identification in FCCX (1/2)Use-case: Brokered identification in FCCX (2/2)Use-case: Student's right to knowUse-case: public-auditability with randomnessResearch in multiplicative complexity (MC)

3 Our perspective on ZKProofOutlineZKProof assessmentZKProof assessment

4 ConclusionsOutlineFinal RemarksThank you for your attention

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