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Enabling Data Confidentiality with Public Blockchains

Edoardo Marangone, Claudio Di Ciccio, Daniele Friolo, Eugenio Nerio Nemmi, Daniele Venturi, Ingo Weber

TL;DR

A formal analysis of the security guarantees of MARTSIA is provided, and the proof-of-concept implementation over multiple blockchain platforms is illustrated, to demonstrate its interoperability.

Abstract

Blockchain technology is apt to facilitate the automation of multi-party cooperations among various players in a decentralized setting, especially in cases where trust among participants is limited. Transactions are stored in a ledger, a replica of which is retained by every node of the blockchain network. The operations saved thereby are thus publicly accessible. While this aspect enhances transparency, reliability, and persistence, it hinders the utilization of public blockchains for process automation as it violates typical confidentiality requirements in corporate settings. To overcome this issue, we propose our approach named Multi-Authority Approach to Transaction Systems for Interoperating Applications (MARTSIA). Based on Multi-Authority Attribute-Based Encryption (MA-ABE), MARTSIA enables read-access control over shared data at the level of message parts. User-defined policies determine whether an actor can interpret the publicly stored information or not, depending on the actor's attributes declared by a consortium of certifiers. Still, all nodes in the blockchain network can attest to the publication of the (encrypted) data. We provide a formal analysis of the security guarantees of MARTSIA, and illustrate the proof-of-concept implementation over multiple blockchain platforms. To demonstrate its interoperability, we showcase its usage in ensemble with a state-of-the-art blockchain-based engine for multi-party process execution, and three real-world decentralized applications in the context of NFT markets, supply chain, and retail.

Enabling Data Confidentiality with Public Blockchains

TL;DR

A formal analysis of the security guarantees of MARTSIA is provided, and the proof-of-concept implementation over multiple blockchain platforms is illustrated, to demonstrate its interoperability.

Abstract

Blockchain technology is apt to facilitate the automation of multi-party cooperations among various players in a decentralized setting, especially in cases where trust among participants is limited. Transactions are stored in a ledger, a replica of which is retained by every node of the blockchain network. The operations saved thereby are thus publicly accessible. While this aspect enhances transparency, reliability, and persistence, it hinders the utilization of public blockchains for process automation as it violates typical confidentiality requirements in corporate settings. To overcome this issue, we propose our approach named Multi-Authority Approach to Transaction Systems for Interoperating Applications (MARTSIA). Based on Multi-Authority Attribute-Based Encryption (MA-ABE), MARTSIA enables read-access control over shared data at the level of message parts. User-defined policies determine whether an actor can interpret the publicly stored information or not, depending on the actor's attributes declared by a consortium of certifiers. Still, all nodes in the blockchain network can attest to the publication of the (encrypted) data. We provide a formal analysis of the security guarantees of MARTSIA, and illustrate the proof-of-concept implementation over multiple blockchain platforms. To demonstrate its interoperability, we showcase its usage in ensemble with a state-of-the-art blockchain-based engine for multi-party process execution, and three real-world decentralized applications in the context of NFT markets, supply chain, and retail.
Paper Structure (29 sections, 1 theorem, 1 equation, 11 figures, 5 tables)

This paper contains 29 sections, 1 theorem, 1 equation, 11 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Example, problem illustration, and requirements
  3. Background
  4. The MARTSIA approach
  5. Workflow
  6. Step 1: System boot
  7. Step 2: Initialization
  8. Step 3: Key management
  9. A note on the privacy of actors and confidentiality of roles
  10. A note on the security of key requests
  11. Step 4: Data exchange
  12. A note on the resistance to key counterfeiting
  13. Data
  14. Summary and considerations
  15. On the design rationale
  16. ...and 14 more sections

Key Result

Theorem 1

Let $\mathsf{ABE}$ be a Multi-Authority Attribute-Based Encryption Scheme with message space $\{0,1\}^*$, authorities $\mathcal{T}$, global identities $\mathcal{R}$ enjoying correctness (def:maabe) and CPA-Security (def:maabe-cpa). Let $\mathcal{P}_1=\mathcal{T}$, $\mathcal{P}_2=\mathcal{R}$, $\math

Figures (11)

  • Figure 1: A multi-party process for the assembly of special car parts
  • Figure 2: The key components and their interactions in the MARTSIA approach
  • Figure 3: The system boot phase in MARTSIA. Dotted lines are added for clarity to indicate that the roles of Reader, Data Owner and Authority are assigned, although no direct message is sent to them by the Attribute Certifiers.
  • Figure 4: Authority initialization and key management phases in MARTSIA
  • Figure 5: The data exchange phase in MARTSIA
  • ...and 6 more figures

Theorems & Definitions (8)

  • Definition 1: UC-Secure MPC
  • Definition 2: UC-Secure MPC in the hybrid model
  • Definition 3: Disjoint Parties UC-Secure MPC in the hybrid model
  • Definition 4: Correctness
  • Definition 5: CPA-security
  • Theorem 1
  • proof
  • Remark 1