Shirtum Will Integrate Chainlink VRF to Secure Randomization (Buybacks incoming)

4 min readJul 14, 2021


We’re excited to announce that Shirtum — a global marketplace of football NFTs — will integrate Chainlink Verifiable Random Function (VRF) on the Binance Smart Chain (BSC) blockchain. By integrating Chainlink’s industry-leading decentralized oracle network, we can obtain access to a tamper-proof and auditable source of randomness needed to fairly select winners from whitelists and to randomize a series of basic NFTs for anyone who joins. Ultimately this creates a more exciting, transparent, and fraud-proof user experience, as users can join different events organized by Shirtum that will allow access to whitelists for the acquisition of exclusive NFTs or prize draws, among other things, where the winners will be chosen in a fair and transparent way thanks to the aforementioned integration.

Shirtum has developed a native app for Android and iOS and a web app where users can buy, sell, collect and exchange football NFTs with exclusive content of iconic moments from the athletes’ history told by themselves.

In order to provide transparency to the selection of prize winners and random entry to the different events that shirtum will organize, we need access to a secure random number generator (RNG) that any user could independently audit. However, RNG solutions for smart contracts require several security considerations to prevent manipulation and ensure system integrity. For instance, RNG solutions using on-chain data like block hashes can be exploited by blockchain miners, while off-chain RNG solutions like traditional data providers are opaque and don’t provide users with definitive proof about the integrity of the process.

After reviewing various solutions, we selected Chainlink VRF because it’s based on cutting-edge academic research, supported by Chainlink’s time-tested oracle infrastructure, and secured through the generation and on-chain verification of cryptographic proofs that guarantee the integrity of each random number supplied to smart contracts.

Chainlink VRF works by combining block data that is still unknown when the request is made with the oracle node’s pre-committed private key to generate both a random number and a cryptographic proof. The Shirtum smart contract will only accept the random number input if it has a valid cryptographic proof, and the cryptographic proof can only be generated if the VRF process is tamper-proof. This provides our users with automated and verifiable assurances directly on-chain that the Shirtum marketplace is provably fair and cannot be tampered with by the oracle, outside entities, or the Shirtum team.

Ahead of us, we still find several other integration opportunities using Chainlink’s services, such as the automatization of the weekly buybacks that we have already established as company policy. We are excited to start this road with one of the biggest players in the Blockchain sphere and confident that this and further integrations will boost Shirtum’s value and improve our users’ experience.

“We want randomness to foster the element of surprise and excitement among our users, and we want them to be sure that this randomness is as fair and transparent as it can be.” — David Rozencwaig, Shirtum’s CEO

About Chainlink

Chainlink is the industry standard oracle network for powering hybrid smart contracts. Chainlink Decentralized Oracle Networks provide developers with the largest collection of high-quality data sources and secure off-chain computations to expand the capabilities of smart contracts on any blockchain. Managed by a global, decentralized community, Chainlink currently secures billions of dollars in value for smart contracts across decentralized finance (DeFi), insurance, gaming, and other major industries.

Chainlink is trusted by hundreds of organizations, from global enterprises to projects at the forefront of the blockchain economy, to deliver definitive truth via secure, reliable oracle networks. To learn more about Chainlink, visit, subscribe to the Chainlink newsletter, and follow @chainlink on Twitter. To understand the full vision of the Chainlink Network, read the Chainlink 2.0 whitepaper.

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