# Anonymous State Pinning for Private Blockchains

## TL;DR

This paper introduces an anonymous state pinning method for private blockchains that enhances privacy and security by preventing transaction rate leaks and allowing contestability, with a cost-effective implementation and hierarchical extension.

## Contribution

The paper presents a novel anonymous state pinning approach for private blockchains that addresses privacy and security limitations of existing solutions, including contestability and cost analysis.

## Key findings

- Pinning a private blockchain once per hour costs approximately US$508 annually.
- The proposed method allows challengeability of pins without revealing private data.
- Hierarchical pinning reduces costs but increases finality times.

## Abstract

Public blockchains such as Ethereum and Bitcoin provide transparency and accountability, and have strong non-repudiation properties, but fall far short of enterprise privacy requirements for business processes. Consequently consortiums are exploring private blockchains to keep their membership and transactions private. However, private blockchains do not provide adequate protection against potential collusion by consortium members to revert the state of the blockchain. To countenance this, the private blockchain state may be "pinned" to a tamper resistant public blockchain. Existing solutions offering pinning to the public blockchain would reveal the transaction rate of the private blockchain, and do not provide a mechanism to contest the validity of a pin. Moreover, they require that all transactions and members of the private blockchain be revealed. These challenges are hampering the wider adoption of private blockchain technology. We describe the primary author's `Anonymous State Pinning approach', which overcomes these limitations and present a security proof to demonstrate pins can be challenged without compromising these properties. We perform a gas cost analysis of the implementation to estimate the operating cost of this technology, which shows that pinning a private blockchain at the rate of one pin per hour would cost US$508 per year. A hierarchical pinning approach is proposed which would allow many private blockchains to pin to a management blockchain which would then pin to Ethereum MainNet. This approach saves money, but at the cost of increased finality times.