A consumer-driven access control approach to censorship circumvention in content-centric networking Jun Kurihara, Kenji Yokota and Atsushi Tagami KDDI R&D Laboratories, Inc. ACM ICN 2016 Kyoto, Japan, Sep. 28, 2016 1 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Outline of my talk 1. Introduction 2. Censorship circumvention in CCN 3. Basics of consumer-driven access control approach 4. Enhancement using manifest and nameless object 5. Conclusion 2 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Introduction 3 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Censorship: A serious problem in networking Censorship in a network: Monitoring network messages, checking ‘ what is requested ’, and dropping messages in the blacklist by a certain authority. Censorship is widely spread now and serious problem in the Internet 4 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Censorship is easily enforceable in CCN Content data itself can be encrypted in a certain AC, but interest name is not. Explicitly-given and semantic name in CCN made censorship trivial. consumer domain: /kddi router Censorship authority publisher • Capture and analyze interests; and • Drop any interests by checking only their names “democracy” domain: /kyoto 5 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Censorship circumvention in CCN 6 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Two types of countermeasures in CCN • Tor-like scheme • Proxy-based scheme • Multi-layered encryption at • Establishing anonymized channel anonymizing routers between proxy and consumer • Significant overhead and delay • Simpler and faster than Tor-like scheme R. Tourani, S. Misra, J. Kliewer, S. Ortegel, and T. Mick, “Catch me if you can: A practical framework to evade censorship in information-centric S. DiBenedetto, P. Gasti, G. Tsudik, and E. Uzun, “AND ā NA: Anonymous networks,” in Proc. ACM ICN 2015 . named data networking application,” in Proc. NDSS 2012 . C. Ghali, M. A. Schlosberg, G. Tsudik, and C. A. Wood, “Interest-based access control for content centric networks,” in Proc. ACM ICN 2015 . 7 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Proxy-based approach Our scheme is basically categorized as a proxy–based scheme Anonymized interest ( /<routable prefix>/ + encrypted name ) domain: /kddi ? (/kddi/democracy.mpg) Trusted proxy encrypt! decypt! interest /kddi/democracy.mpg plaintext name Communication via encrypted name 8 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Cache recycling problem of proxy-based approaches Anonymized communication is established between each consumer and a proxy under distinct encryption key. Anonymized communication channel Consumer A Consumer B Standard CCN behind the proxy The same content is queried via different names by different users Cached content never be recycled 9 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Basics of consumer-driven access control approach 10 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
System model Entity: CCN basic parties + cache enablers E i + anonymizer A + attacker • cache enabler E 2 (as a router) anonymizer A (trusted proxy) consumers attacker publisher (as a router) domain: /kddi CCN router cache enabler E 1 (as a router) Content names follow a conventional (ICN) hierarchical naming scheme like • URL (e.g., /kddi/demo/video.mpg). 11 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Attacker definitions We consider two types of attackers. Stronger version Passive Attacker Active Attacker Capture/analyze interests Capture/analyze interests Modify interests Learn “ what is requested ” • and “ who is requesting ”; Masquerade as legitimate Drop/filter interests • consumers *Passive ⊃ Active 12 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Key elements of our approach [Against passive attacker] (1) Encryption-based access control to interest names for cache enablers and anonymizer [Against passive/active attacker] (2) Authentication and decryption with hidden consumer ID at cache enablers and anonymizer 13 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
(1) Encryption-based access control to names: Preliminary Access control: A technique used to regulate who or what can view raw/original data in a computing environment. Encryption-based access control: Data is encrypted in such a way that only authorized users are allowed to decrypt the encrypted data and obtain the raw data. With Encrypted valid key data Possibly different With no key With valid key Assigned decryption keys are identified as access rights 14 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
(1) Encryption-based access control to names: Overview of the approach Consumer grants access rights to original interest names to cache enablers E i and anonymizer A via the encryption-based access control Assign key for E 2 Assign key for A E 2 Assign key for E 1 anonymizer A domain: /kddi cache enabler E 1 15 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Consumers encrypts interest names in such a way that pre-authorized E i and A can decrypt them and obtain original names. [Processing incoming interest at E i ] Anonymized interest (/routable prefix/ + encrypted name) (1) Decrypt (/kddi/democracy.mpg) (/kddi/democracy.mpg) /kddi/democracy.mpg Qualified (2) CS search with original name cache enabler E i CS /kddi/democracy.mpg (3) Respond by encrypted name (/kddi/democracy.mpg) content object *** illustrated only the case of cache hit for simplicity. *** 16 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
[Processing incoming content at E i ] (simply the dual of interest case) content object (/kddi/democracy.mpg) (1) Decrypt (/kddi/democracy.mpg) Qualified cache enabler E i /kddi/democracy.mpg (2) Cache with original name for recycle CS /kddi/democracy.mpg [Key observation] Access control to interest names ↔ Access control to cache-recycling opportunities *** omitted the process of PIT entry consumption for simplicity. *** 17 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
(2) Authentication and decryption with hidden ID: Preliminary [Observations] E i and A must learn the consumer ID from an interest to find a consumer specific key(s) for name decryption and interest authentication via HMAC/signature Consumer ID itself leaks the consumer information to attackers [Requirements] Consumer ID must be included and hidden in interests • Only cache enablers and anonymizer learn the ID from an interest for • decryption and authentication 18 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
(2) Authentication and decryption with hidden ID: Overview of the approach Anonymizer uses a public key broadcast encryption for hiding IDs in interests. Decryption keys are assigned to cache enablers • Public (encryption) key is published. • Having public key Assign key for E 2 Store key for A E 2 Assign key for E 1 anonymizer A domain: /kddi Having public key E 1 19 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Consumer generates the anonymizing interest from the encrypted name as: Broadcast public key from A (/kddi/democracy.mpg) (Consumer ID) HMAC Encrypted ID Encrypted name HMAC generation by name encryption key 20 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
E i and A authenticate and generate the incoming interest as: (/kddi/democracy.mpg) (Consumer ID) HMAC Encrypted ID Encrypted name Assigned broadcast decryption key Consumer ID Retrieve the name encryption key associated to the ID from key storage Decrypt! Authenticate! 21 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Advantage and disadvantage [Security for passive attacker] • No leakage about content name (what) • No leakage about consumer identity (who) [Security for active attacker] • Interest modification can be detected 22 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
[Efficiency] • In-network caching can be fully leveraged at cache enablers E i ’s and anonymizer A • More beneficial as # of E i ’s increases. trade-off between cache recycling opportunity and overhead • Cryptographic operations (access control and authentication) at E i and A may involve serious computational cost. • More serious overhead as # of E i ’s increase. 23 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
This problem is solved by combining our approach with manifest and nameless objects. We minimize the overhead with maintaining the security and maximizing the benefit of in-network caching. 24 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Enhancement using manifest and nameless object 25 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
Preliminary: Manifest and nameless objects in CCNx Manifest : Content object providing a list of content objects (names and hashes) Manifest structure content object catalog Names Hashes /kddi/democracy.mpg/1 0xABCD /kddi/democracy.mpg/2 0x1234 /kddi/democracy.mpg/3 0xA1B2 … … Guarantee of integrity and unforgeability Additional information (e.g., decryption key name/hash) signature Listed items can be authenticated only by lightweight hash verification. Manifest-based content retrieval: Consumer first obtain and parse manifest, then retrieve listed content objects. 26 Sep. 28, 2016 Jun Kurihara (KDDI R&D Labs.)
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