Aleph.im Verifiable Random Function (VRF)

Clément Fermaud
Aleph.im
Published in
6 min readSep 12, 2023

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TL;DR

Verifiable Random Functions (VRF) are cryptographic primitives that generate random numbers that are both unpredictable and verifiable. Essential in applications requiring trust and decentralization, VRFs ensure a unique and auditable random output for each input. This article delves into the definition of VRFs, their utility, application in blockchain technology, and a detailed explanation of aleph.im’s proposed VRF solution.

What is a Verifiable Random Function (VRF)?

A Verifiable Random Function (VRF) is a cryptographic construct that embodies a fusion of mathematical and cryptographic principles to serve a specific purpose: generating outputs that are both pseudorandom and verifiable. In layman’s terms, it’s a black-box machine that takes an input and churns out a number that looks random to the outside world. However, unlike simple random number generators, VRF provides cryptographic assurances that make it unique and indispensable in secure, decentralized systems.

Unique Features:

Uniqueness: In a VRF, each unique input leads to a unique output.

Verifiability: The magic of VRF lies in its ability to produce a proof alongside the random number. This proof can be verified by anyone possessing the corresponding public key. This adds a layer of credibility to the output, ensuring that it was generated in an honest and secure manner. Verifiability is particularly vital in systems where transparency and trust are required and A full reveal of the process is not an issue with the aleph.im VRF implementation.

Pseudorandomness: While the output is deterministic for a given input and private key, it appears random to those without access to the private key. This pseudorandomness ensures that while the process is repeatable and verifiable, it is not easily predictable or manipulatable by malicious actors. The property of pseudorandomness makes VRFs useful in scenarios where fairness is a concern, such as in the selection of validators or leaders in blockchain networks.

The intricate blend of these features — uniqueness, verifiability, and pseudorandomness — creates a secure and reliable mechanism that serves as a cornerstone for applications and systems where integrity and transparency are non-negotiable.

VRFs are integral to a variety of applications where trust, security, and transparency are critical. They are essential for enhancing internet security, specifically in securing domain name system (DNS) messages. VRFs are also pivotal in zero-knowledge technology protocols, providing a foundation for proofs and databases where data can be verified without being exposed.

Their utility extends to non-interactive lottery systems, where they ensure provably fair outcomes, and to verifiable transaction escrow schemes, which maintain user anonymity. In decentralized systems and blockchain networks, they contribute to trustworthy random number generation and are used in consensus algorithms for the random selection of validators or miners. Additionally, VRFs play a role in secure multi-party computations and systems requiring high-level transparency and third-party auditing. Overall, the versatility and security features of VRFs make them indispensable across multiple domains.

How Blockchains Use VRF?

In blockchain technology, Verifiable Random Functions (VRFs) serve several distinct but interconnected purposes that collectively enhance the integrity, security, and functionality of the system.

  • Random Beacon Chains: Some blockchains like Dfinity use VRFs to generate a random beacon, which serves as a secure and unpredictable value at regular intervals. This random beacon is then used for various tasks such as chain extensions, adding an extra layer of security and unpredictability to the network’s operation.
  • Proof of Stake Systems: In consensus models like Proof of Stake (PoS), the selection of validators can be a point of vulnerability if not executed properly. VRFs address this by enabling a random yet verifiable selection of validators who are responsible for adding new blocks to the blockchain. This randomness makes the PoS system more resistant to manipulation and ensures a fair, decentralized process.
  • Smart Contracts: VRFs are increasingly being incorporated into smart contracts, particularly those related to decentralized applications in the fields of gaming and lottery systems. By using VRFs, these contracts can generate random numbers that are not only unpredictable but also verifiable, ensuring that the outcomes are fair and haven’t been tampered with.
  • Transaction Ordering: Front-running attacks, where an attacker gains advance knowledge of transactions to manipulate the order for their benefit, can be detrimental in a blockchain network. VRFs are used in some blockchain architectures to randomly determine the order of transactions within a block. This randomness, which is also verifiable, serves as a protective measure against such exploitative practices.

The incorporation of VRFs into these aspects of blockchain technology highlights their importance in ensuring that these systems are both secure and functionally robust. By using VRFs, blockchains are better equipped to maintain their decentralized nature while providing a secure, transparent, and equitable environment.

Aleph.im’s VRF Solution

Aleph.im aims to set a new standard in Verifiable Random Functions (VRFs) by combining Virtual Machines (VMs), Aleph Messages, and peer-to-peer (p2p) messaging to achieve trustless randomness. This endeavor is particularly significant given the critical role VRFs play in oracle networks, serving as the backbone for generating trustworthy random numbers.

Requirements and Desired Features

Aleph.im’s VRF solution targets uniformly distributed randomness that is both tamper-proof and secure. The solution aims for unpredictability and ideally seeks mathematical proofs for its security features. Additional considerations for the solution include high robustness to nodes (VMs) dropping out or denying service, minimal communication overhead, public verifiability, and a straightforward implementation process.

Solution Overview

The VRF mechanism in aleph.im revolves around the concept of a “VRF coordinator,” responsible for orchestrating the generation of random numbers. The process is initiated when a client requests a random number from the VRF, either through a hosted service or a library.

Upon receiving this request, the VRF coordinator selects a set of compute resource nodes (CRNs). Each of these CRNs generates a random number and computes its hash using SHA3–256. These hashes are then posted to aleph.im using a POST message, which also includes a unique request identifier. Once all the hashes are posted and confirmed, the coordinator requests the actual random numbers from each node.

In the final step, the VRF coordinator performs a verification process to ensure that all random numbers correspond to their previously posted hashes. The random numbers are then combined using an XOR operation to generate the final random number. This final number, along with a summary of operations performed, is published on aleph.im for public verification.

Flexibility and Customization

What sets aleph.im’s VRF apart is the flexibility it offers users. Clients have the option to deploy their own VRF nodes or use a VRF coordinator provided by aleph.im. Furthermore, aleph offers SDK libraries that enable users to check the results and generate the final random number on their own if they prefer.

The solution’s design ensures that if a response from all CRNs is not received, the result is considered inconsistent and invalid. In such cases, the entire procedure halts, and the client must initiate the process again.

The implementation of Verifiable Random Functions (VRFs) is a critical development for enhancing both security and operational capabilities. Aleph.im’s VRF solution, with its integration of Virtual Machines, Aleph Messages, and peer-to-peer communication, offers a comprehensive approach that meets stringent requirements for security, unpredictability, and public verifiability. The architecture of Aleph.im’s system provides an array of options for user engagement, facilitating a level of customization that serves diverse use-cases and stakeholder needs.

Conclusion

The deployment of this VRF solution by aleph.im serves as an illustrative example of how decentralized systems can achieve heightened levels of integrity, particularly in applications requiring random number generation. This development aligns with broader trends in the blockchain industry that are focused on transitioning from traditional trust-based systems to models substantiated by mathematical and cryptographic proofs.

For developers and parties interested in decentralized technologies, aleph.im’s VRF framework offers a valuable reference point for constructing secure, transparent, and verifiable systems. The solution contributes to the ongoing dialogue and technological evolution aimed at enhancing the reliability and integrity of decentralized networks.

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