Privacy in Content Oriented Networking: Threats and countermeasures

Abdelberi Chaabane, Emiliano De Cristofaro, Mohamed Ali Kaafar, and Ersin Uzun

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3 Interconnecting information2 Interconnecting hosts1 Interconnecting wires

Telephony TCP/IP

A brief History of networking

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Change in Communication Paradigm

• Today Internet struggles – Scalability– Mobility– Security

• Move to Content-oriented Network– Traffic is already content-oriented

• CDN, overlays, P2P– Users/applications care “what to receive”

• They don’t care “from whom”• Host based communication model is getting ‘’outdated’’

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Notable Content Oriented Networking Architectures

NetInfNetwork of Information

DONA

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Macro-building blocks

• Named Content– Objects are named to facilitate data dissemination and

search • Content Based Routing– Routing content rather than host

• Content Delivery– Using multipath routing and leveraging in network

caching• In Network caching– All components provide caching capability

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CCN Operations

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Contributions

• Systematic study of privacy challenges in CON– Exposing several worrisome issues– Proposing some countermeasures– Highlighting open problems

• Comparing CON to Today’s Internet (TI) from a privacy perspective

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Outline

1. Privacy challenges in CONCache privacyContent PrivacyName privacySignature privacy

2. The potential of CON privacyAnonymityCensorship ResistanceUntraceabilityData authenticity and confidentiality

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CON PrivacyCache Privacy

-Data is cached in every hop

-Infer who consumed what

Name Privacy

-Names are related to the content

- Infer what a user is consuming

Signature Privacy

-Content is signed

- Identify the communicating parties

Content Privacy

-Encryption is not mandatory

-Publicly available content spied on / censored

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Timing attackRTTS

RTTCFetch the targetedcontent RTTt

1. If |RTTt -RTTc| < ε: Content has been fetched by a neighboring consumer

2. If RTTt > RTTc and RTTt < RTTs: Content has been recently fetched from the source

3. Otherwise: The target content has not been consumed

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Potential Solution

• Wait before reply– When a content m is fetched, the corresponding RTTm is stored

– All subsequent requests to m are delayed with RTTm

1. Increased the delay1. It provably achieves perfect privacy[1]

2. No assumption about content correlation/ Network topology

3. Reduced bandwidth

1: Acs, G., Conti, M., Gasti, P., Ghali, C., & Tsudik, G. Cache Privacy in Named-Data Networking. ICDCS’13.

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Potential Solution

• Delay the first K– When a content m is fetched, the corresponding RTTm is stored and a

random number K is chosen – K subsequent requests to m are delayed with RTTm

1. Assumption about content correlation

2. Increased delay for non popular content

1. Popular content is not delayed2. Formal model to quantify the

tradeoff privacy/latency [1]3. Reduced bandwidth

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Potential Solution• Collaborative caching– Multiple caches collaborate to create a distributed cache

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Potential Solution• Collaborative caching– Multiple caches collaborate to create a distributed cache

1. Administrative collaboration 2. Potential Delay

1. Increases the anonymity set2. Increases hit rate

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Content Based Monitoring and Censorship

• CON routers – Long-term storage– Computationally powerful

• ‘Less’ powerful adversary is needed to perform censorship

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Potential Solution

• Broadcast encryption– The producer send an encrypted message to a set of users N – Only users in N can decrypt the message

1. Producer generate/store N keys

2. Producer public key and cipher text are of size of O(√N)

1. Content is encrypted once2. Caching is preserved 3. Fine grained user control

(revocation)

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Potential Solution

• Proxy re-encryption

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Potential Solution

• Proxy re-encryption

1. Asymmetric encryption 1. Content is available for any user

2. Content is encrypted once3. Caching is preserved4. Fine grained user control

(revocation)

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Monitoring/Tracking

• Content name are semantically correlated with the content– E.g. /US/WebMD/AIDS/Symptoms/html

• Unlike HTTPS, content name is not encrypted as they are used for routing

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Potential Solution

• Bloom Filter– Using Bloom filter to obfuscate

the content name:• A hierarchical Bloom filter for routing table• A counting Bloom filter for each forwarding

interface

1. Introduce false positives2. BF require periodic resetting

1. Obfuscates content name2. Small architectural changes3. Reduce the size of

routing/forwarding tables

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Censorship/ Monitoring

• Signature is used to provide guarantee on provenance and integrity

• This signature can be used to censor/monitor the content.

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Potential Solution

• Group Signature

• Group Signature

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Potential Solution

• Group Signature– Hide the signer in a set of potential signers (signer ambiguity)

Group Manager

Pub Key

Priv Key

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Potential Solution

• Group Signature– Hide the signer in a set of potential signers (signer ambiguity)

1. Presence of a group manager2. Censorship possible

1. Signature still verifiable2. Efficient

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Potential Solution

• Ring Signature– Hide the signer in a set of potential signers (signer ambiguity)– Signature is generated from the signer private key and a set of

public key

Pub Key

Priv Key

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Potential Solution

• Ring Signature– Hide the signer in a set of potential signers (signer ambiguity)– Signature is generated from the signer private key and a set of

public key

1. Communication overhead linear in the size of the ring

2. Censorship possible

1. Signer anonymity protected2. Trustful content (as long as all signers are trustworthy)

3. No signers interaction / No group manager

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Outline

1. Privacy challenges in CON1. Cache privacy2. Content Privacy3. Name privacy4. Signature privacy

2. The potential of CON privacy1. Anonymity2. Censorship Resistance3. Untraceability4. Data authenticity and confidentiality

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Anonymity

A Trusted Anonymzing proxy Natively provided by the architecture (no SRC/DST)

- A single point of failure- A Local adversary could monitor all the traffic

Mix Networks e.g. Tor• 3 Hops to the source• Low latency

Mix Networks: ANDaNA[2]• 2 Hops to the source• Low latency• Partially disable CON

caching• CCNx specific

Internet CON

[2] ANDaNA: Anonymous named data networking application. DiBenedetto, S., Gasti, P., Tsudik, G., & Uzun, E. NDSS'12

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Censorship

DNS Tempering Effective in some CON

Easier in CON:• Name/Content are not

encrypted• No need for specialized

hardware

At a single router, censorship appears to be easier in CON

Internet CON

Host blacklisting Content (name) blacklisting

DPI (Content blacklisting)• Strong adversary• specialized Hardware

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Tracking

Cookies

• No same origin policy• Only dynamic content can

be tracked• Business model

migration ?

CON is more resilient to tracking but poses new challenges

Internet CON

-More difficult to carry (no addresses + caching)• How to handle security

incident ?

• Using IP and host fingerprinting

Stateless Tracking

• Widespread • Efficient • Tailored to the business

model

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Data authenticity and confidentiality

One size fits all (SSL)• Well studied • Highly optimized

End to End trust model • Different consumer =

different trust model• Widely accepted (PKI) or

new trust management model

Internet CON

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Take home messages

• Content Oriented Networking PrivacyMore resilient to tracking‘’Weak’’ anonymity as native feature

Possibly more vulnerable to censorship Some privacy challenges due to caches, naming, signatures

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