Thursday 06 March 2025
Secret Santa has long been a beloved holiday tradition, but playing it on blockchain technology has its own unique set of challenges. A new paper proposes a solution that leverages zero-knowledge proofs to establish gift sender/receiver relations while maintaining the sender’s confidentiality.
The main issue with playing Secret Santa on-chain is the lack of private computations. The Ethereum blockchain is open and transparent, making it difficult to conceal participants’ identities. To solve this problem, the protocol uses a transaction relayer in conjunction with zero-knowledge proofs to verify that participants belong to the initial set of players.
The setup process requires all participants to register their addresses publicly in a smart contract. This step can be done only once, allowing the same set of participants to play multiple games. The lead participant can register all players in a single transaction safely on their behalf.
The first step of the protocol is called signature commitment. Here, each participant signs a message with their Ethereum address and a unique event ID. The hash of this signature is then stored in a sparse Merkle tree under the corresponding index. This step ensures that participants use deterministically derived ECDSA signatures, preventing non-deterministic attacks.
In the second step, known as gift sender determination, every participant anonymously adds their randomness to an array of gift senders. Each participant generates a unique RSA public key and uses it to encrypt the receiver’s delivery address. The protocol then verifies that the sender has not chosen themselves and that the randomness is unique.
The final step, gift receiver disclosure, assigns the receiver’s address to the corresponding sender’s randomness. To prevent frontrunning attacks, participants can only disclose their receiver once. If a participant tries to disclose twice, their transaction will be reverted.
One of the key security assumptions of the protocol is that each gift sender will not disclose themselves and the randomness used in the second step. Additionally, the ECDSA signature must be constructed following a specific standard, and the event ID must be unique for every game.
The soundness of the protocol relies on the soundness of the underlying zero-knowledge proving system. If participants provide encrypted payloads, they are responsible for ensuring the correctness of the encrypted data.
This innovative approach to Secret Santa on blockchain technology has significant implications for decentralized gift-giving. By leveraging zero-knowledge proofs and sparse Merkle trees, the protocol ensures that gift senders remain anonymous while maintaining the integrity of the game. With this solution, participants can enjoy a fun and secure holiday experience without sacrificing their privacy.
Cite this article: “Secure Secret Santa on Blockchain: A Zero-Knowledge Proof Solution”, The Science Archive, 2025.
Blockchain, Secret Santa, Zero-Knowledge Proofs, Ethereum, Smart Contract, Private Computations, Merkle Tree, Ecdsa Signatures, Rsa Public Key, Frontrunning Attacks
Reference: Artem Chystiakov, Kyrylo Riabov, “ZK Secret Santa” (2025).
