take two curves and call me in the morning: the story of the nsas dual_ec_drbg and its implications...

Take Two Curves and Call Me in the Morning: !

The Story of the NSA’s Dual_EC_DRBG and its Implications to Health Privacy

Aleksander Essex, Ph.D Assistant professor, Western Engineering

Feb. 13th, 2014 !

Talk outline 1. Emergence of the state-level cyber threats

2. Background on Dual_EC_DRBG

3. The backdoor

4. The backlash

5. Lessons for health privacy

Emergence of state-level cyber threats

A new world • Early 2013: Edward Snowden begins working

with reporters

• June 2013: First reports published in media of mass surveillance program by NSA

• December 2013: Only 1% of documents published….

State-level adversaries

Mass Surveillance • Surveillance of communication networks

• PRISM, ECHELON, etc

• Data vs. metadata

State-level adversaries

http://electrospaces.blogspot.ca/p/nicknames-and-codewords.htmlhttp://icons.iconarchive.com/icons/icons-land/vista-hardware-devices/128/Portable-Computer-icon.png

ANT Catalogue • Attacks end-points

• Exploits for major software, hardware, firmware • Examples: DROPOUTJEEP, IRATEMONK, IRONCHEF, DEITYBOUNCE

State-level adversaries

http://electrospaces.blogspot.ca/p/nicknames-and-codewords.htmlhttp://icons.iconarchive.com/icons/icons-land/vista-hardware-devices/128/Portable-Computer-icon.png

State-level adversaries

http://leaksource.wordpress.com/2013/12/30/nsas-ant-division-catalog-of-exploits-for-nearly-every-major-software-hardware-firmware/

Hijacking Standards • Public attempt to backdoor crypto in 90’s

(clipper chip)

• Secretly backdooring crypto standards a new attack vector

State-level adversaries

http://findicons.com/icon/15313/users_2?id=403108

Public

Background on Dual_EC_DRBG

Background • Random numbers important to cryptographic

protocols

• Used for generating keys, nonces, initialization vectors, etc.

• Deterministic random bit generators (DRBG) generate random-looking bits based on algorithm

Dual_EC_DRBG Background

Background • NIST Special Publications: effort to

standardize DRGB and entropy sources

• Used for FIPS validation. Required to sell security products to gov’t clients

• NIST SP 800-90A specified four DRBGs based on different primitives: block ciphers, HMACs, hashes, and elliptic curves

Dual_EC_DRBG Background

Elliptic curves

Dual_EC_DRBG Background

Elliptic curves • Points P, Q: points on the curve

• Point operations: a number times a point equals another point, P = nQ

• Discrete log problem: • Easy to compute P=nQ given n,Q

• Hard to compute n given P,Q

Dual_EC_DRBG Background

DUAL_EC_DRBG

Dual_EC_DRBG Background

a

b

c

. . .

f(aP)

f(bP)

f(cP)

a’

b’

c’

. . .

f(aQ)

f(bQ)

f(cQ)

DUAL_EC_DRBG

Dual_EC_DRBG Background

a

b

c

. . .

f(aP)

f(bP)

f(cP)

a’

b’

c’

. . .

f(aQ)

f(bQ)

f(cQ)

• Internal state: a,b,c…Updated using P

• Output bits: a’,b’,c’…Updated using Q

DUAL_EC_DRBG

Dual_EC_DRBG Background

a

b

c

. . .

f(aP)

f(bP)

f(cP)

a’

b’

c’

. . .

f(aQ)

f(bQ)

f(cQ)

• MUST HAVE property: can’t predict predict next output from previous output

DUAL_EC_DRBG

Dual_EC_DRBG Background

a

b

c

. . .

f(aP)

f(bP)

f(cP)

a’

b’

c’

. . .

f(aQ)

f(bQ)

f(cQ)

• MUST HAVE property: can’t predict predict next output from previous output

• You COULD if you knew the internal state…

The backdoor

The backdoor • Recall P,Q are points on the curve

• That means there is a number n such that P=nQ

The backdroor

The backdoor

The backdroor

a

b

c

. . .

f(aP)

f(bP)

f(cP)

a’

b’

c’

. . .

f(aQ)

f(bQ)

f(cQ)

• Attack: recover internal state

• Use magic number n: n*(aQ) = a*(nQ) = aP

• With aP, can compute b’, c’, … all future values

TLS: we all use it every day

The backdroor

Dual_EC_DRBG

Nonce

Nonce

TLS “ClientHello”

Dual_EC_DRBG

premaster secret

TLS ClientKeyExchange

Encpk(premaster secret)

Sees Dual_EC_DRBG output Computes internal state

Use internal state to compute next output (i.e., premaster secret and hence encryption keys)

The backdoor • If P,Q generated randomly, DUAL_EC_DRBG

is secure. If P chosen as P=nQ, a backdoor exists

• Who generated P,Q in SP 800-90A? NIST?

• No. Rather NSA, it would seem

The backdroor

The backlash

NIST’s initial response

The backlash

There has been some confusion about the standards development process and the role of different organizations in it. NIST’s mandate is to develop standards and guidelines to protect federal information and information systems. Because of the high degree of confidence in NIST standards, many private industry groups also voluntarily adopt these standards. !!

http://www.nist.gov/director/cybersecuritystatement-091013.cfm

Then…

The backlash

http://csrc.nist.gov/publications/nistbul/itlbul2013_09_supplemental.pdf

“ NIST strongly recommends that, pending the resolution of the security concerns and the re-issuance of SP 800-90A, the Dual_EC_DRBG, … no longer be used.

Who implemented it?

The backlash

http://csrc.nist.gov/groups/STM/cavp/documents/drbg/drbgval.html

Who implemented it?

The backlash

http://csrc.nist.gov/groups/STM/cavp/documents/drbg/drbgval.html

Who implemented it?

The backlash

http://csrc.nist.gov/groups/STM/cavp/documents/drbg/drbgval.html

!

• These companies received FIPS validation for Dual_EC_DRBG implementations

• Does not mean Dual_EC_DRBG enabled by default, used, or even compiled in respective products

http://www.reuters.com/article/2013/12/20/us-usa-security-rsa-idUSBRE9BJ1C220131220

Was it anyone’s default?

• Yes. NSA paid RSA $10M to make Dual_EC_DRBG the default in their BSAFE security suite

Backlash • Dual_EC_DRBG pulled by NIST (for now)

• Code yanked from most products

• Researchers boycotting upcoming RSA conference

• Long term credibility issues for NIST

The backlash

Implications • Only those with knowledge of P=nQ

relationship can exploit this (i.e., NSA)

• CSEC played a role in this story

The backlash

Lessons for health privacy

Lesson 1: It takes a scandal • 2004: Certicom knew this could happen.

Filed a patent to generate P,Q randomly (see USP 8,396,213)

• 2005: NIST knew this could happen (according to John Kelsey in late 2013)

• 2007: Microsoft researchers knew this could happen. Gave talk at CRYPTO ‘07

Lessons for health privacy

Lesson 2: Nothing is sacred • Healthcare data cannot be considered

exempt from interference from state-level actors

• Risk assessments must factor them in (as hard as it is to do)

• CSEC’s relationship with PHIPA unclear

Lessons for health privacy

Lesson 3: Vendors not necessarily working in your interest • Vendors may be cooperating with state-level

actors (voluntarily or involuntarily)

• Verify security claims with SME’s

Lessons for health privacy

Lesson 4: Trust standards only as far as you can throw them • NIST has credibility issues

• Algorithm isn’t necessarily the problem, parameters are

• Need more research into verifiably random parameter selection

Lessons for health privacy

Conclusion • As an organization sharing health data, what

should you do?

• Dual_EC_DRBG fallout seems contained for now, but points to a sinister future

• Healthy dose of skepticism warranted

• Conversation about health data privacy in the face of state-level actors needs to start

Lessons for health privacy