1. PACE: An Architectural Style for Trust Management in Decentralized Applications Girish Suryanarayana Justin Erenkrantz Scott Hendrickson

2. Motivation Decentralized architectures and systems Absence of trusted central controlling authority Everyone makes local autonomous decision Determines validity of information received Protect against malicious peers External vs Internal Architecture External facilitates interaction between peers Internal controls behavior of peer

3. Threats of Decentralization Impersonation Fraudulent Actions Misrepresentation Collusion Denial of Service Addition of Unknowns Deciding whom to trust Out of band knowledge ● Need policies to help address these threats

4. PACE Architectural Style Constraints on the architecture Identities Explicit Trust Comparable Trust Separation of Internal and External Data Dependencies of Layers Communication, Information, Trust, and Application Implicit Trust

5. Internal Architecture in PACE Communication Layer Information Layer Trust Layer Application Layer Communication Manager External Information Internal Information Key Manager Signature Manager Trust Manager Application Trust Policy HTTP SenderCustom ProtocolsMulticast Manager Multicast Handler Credential Manager A P P L I C A T I O N C2 asynchronous events Requests/Notifications Communication layer: All communication Information layer: All data storage Trust layer: Generation of trust values Application layer: Domain-specific Sub-architecture

6. Decentralized Auction Alice Bob Carol Bid ($20/unit) Sell Advertise (10 units) Bid ($25/unit) Bob trusts Alice = t ba (Bids) = 0.4 Bob trusts Carol = t bc (Bids) = 0.8 Alice trusts Bob = t ab (Sell) = 0.8 Carol trusts Bob = t cb (Sell) = 0.8 Ordering of Events: 1. Bob advertises to Alice and Carol 2. Alice and Carol respond with bids 3. Bob trusts Carol more than Alice 4. Bob decides to sell to Carol even though Alice offers a higher bid. Alice, Bob, and Carol No controlling authority Java prototype created Multicast comm. used Created GUI

7. Conclusions Integrate communication, data, and trust models Supports dynamic architectures Threats of decentralization can be addressed as long as PACE constraints are strictly followed a suitable trust model is adopted Experimented with a decentralized auction Created Java framework for PACE Illustrated the feasibility Looking for more experiments and usage