Secure Cloud Storagemeets with

Secure Network Coding

Fei Chen (Chinese University of Hong Kong, Hong Kong)

Tao Xiang (Chongqing University, China)

Yuanyuan Yang (Stony Brook University, USA)

Sherman S. M. Chow (Chinese University of Hong Kong, Hong Kong)

Roadmap• Preliminaries• Generic Construction

• Technical Obstacles

• Showcase: A Novel Protocol• Extensions

• Third-party Auditing• User Anonymity

• Summary

Secure Cloud Storage (SCS)

• Juels-Kaliski, Ateniese et al. (both CCS’07)• Wang, Chow, Wang, Ren, Lou (IEEE TC’13)• Yang-Jia (TPDS’13)• Wang, Chow, Li, Li (ICDCS’13)

SCS Protocol

User

Cloud

Handling Security

User

Cloud

Security Definition

Secure Network Coding (SNC)

• Ahlswede, Cai, Li, Yeung from CUHK (IEEE TIT’00)• Li, Yeung, Cai (IEEE TIT’03); Cai-Yeung (ISIT’02)• Gkantsidis-Rodriguez (INFOCOM’06); Li, Lui, Chiu (ICNP’06)• Agrawal-Boneh (ACNS’09); Catalano et al. (PKC’12)• (many others)

SNC Protocol

Security Definition

OUR WORK

1. Generic Construction

Basic Idea

Optimization

Security

Data Recovery Algorithm

2. A Novel SCS Protocol• Based on a recent SNC protocol by Catalano et al.

(PKC’12)

• First publicly verifiable secure cloud storage protocol which is provably secure (not random oracle heuristics)

Detailed Construction

Theoretical Performance• Asymptotic performance comparable to previous work

Experimental Performance• Benchmark (data from Wikipedia)

• Storage and communication overhead

Computation Cost• (Time is in milliseconds.)

• The protocol is effective in practice.• Efficiency cost is acceptable for a standard model proof.

• For protocols with security argued with random oracle heuristics, one may instantiate with larger cryptographic groups / security parameters, which results in lower efficiency anyways.

Supporting Third-Party Auditing

• Idea: mask the returned result with randomized vectors with coefficients all 0 (zero-knowledge proof of knowledge)

• [Wang, Chow, Wang, Ren, Lou (IEEE TC’13)]

Supporting User Anonymity

• Idea: randomization again (blind signature approach)• [Wang, Chow, Li, Li (ICDCS’13)]

Summary• Secure Cloud Storage meets with Secure Network Coding

• A generic construction

• A novel SCS protocol

• Security definition and security proof

• Support of third-party auditing and user anonymity