An improved method for privacy-preserving web-based data collection - - PowerPoint PPT Presentation

An improved method for privacy-preserving web-based data collection

Riivo Talviste Supervisor: Dan Bogdanov, MSc

April 24, 2009

Outline of the Talk

• State of the Art
• Problem statement
• Improved architecture
• Implementation
• Demo

The Danisco Auction (1)

• In Denmark farmers grow sugar beets, which

they sell to the Danisco company.

• EU reduced support, so they conducted a

nation-wide double auction.

• A survey showed that farmers really care about

their confidentiality.

Survey Results

Agree strongly Agree Don't know Disagree Disagree strongly 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% 35% 43% 18% 2% 1%

It is important that my bids are kept confidential

The Danisco Auction (2)

• Auctioneer = {Danisco, DKS, SIMAP project}
• The first large-scale practival application of

multiparty computation (MPC).

• Held in two phases:

– Placing and gathering bids, – Processing bids and calculating market clearing

price (MCP).

The Danisco Auction Architecture

Danisco website Farmer's computer Web server

session Java applet public keys encrypted shares database

Danisco DKS SIMAP

MPC

Phase 1 Phase 2

login

Problem Statement

• Farmer has to trust the web server

unconditionally, as it can send wrong public keys.

• Java applet is a fat-client application, not

everybody has Java Runtime Environment (JRE) installed.

Our Solution

• Similar to the Danisco auction architecture.
• Built on the Sharemind framework.

Our Architecture

client's computer Web server

Flex application

Miner 1 Miner 2 Miner 3

MPC share share share

HTTPS connection

Miner 1 web server Miner 2 web server Miner 3 web server

Security Analysis

Confidentiality is satisfied by:

• Secret sharing
• Public Key Infrastructure (PKI) and direct

HTTPS connections.

– Client does not have to trust anybody

unconditionally

– Potential security risk: malicious miners with

certificates already trusted by client are still a threat.

Implementation

• Adobe Flex technology

– Free, open source framework, – MXML, a XML-based language for layout, – ActionScript 3, an object-oriented language for

client logic,

– Thin-client, – Run by Adobe Flash Player.

• Recent survey shows that 99.0% of Internet-

enabled desktops have Flash Player.

Demo

Conclusion

• First large-scale practical MPC applications are

already in use.

• We proposed an architecture with stronger

confidentiality guarantees than the ones currently in use.

• We implemented it using Adobe Flex, the most

spread web-based software platform.

Questions!? Thank You!