DropKick ⚽️ - A minimal commit/reveal PQ rescue protocol

The protocol leverages blockchain technology's inherent trustless timestamping capabilities to securely encode a commitment which can later be revealed to facilitate the transfer of legacy coins into a new PQ-secure wallet. This commitment, represented as H(H(w, Q), Q) within a block, uses a post-quantum public key Q and a witness w to a one-way function f. At the time of coin spend, the presence of this witness, along with a signature from Q, authorizes the transaction. Verifiers subsequently confirm the validity and timing of the commitment opening, ensuring the calculated s = f(x) is correct and validating the PQ-signature from Q.

DropKick distinguishes itself by accommodating various one-way functions and does not necessitate the confiscation of coins, applying exclusively to UTXOs with decidable knowledge asymmetries. Its design minimizes impact on the blockchain until the reveal phase, where proofs of commitment opening are added, consuming minimal space and resources. This protocol does not require users to possess their own PQ-safe UTXOs, instead allowing the use of third-party aggregators to manage these commitments collectively. Despite its simplicity and reduced security compared to Tadge Dryja’s Lifeboat/Lifejacket protocols — which demand validators index all commitments for chronological ordering — DropKick uses Merkle trees to embed commitments indirectly through blocks, thus eliminating the need for centralized indexing and reducing on-chain visibility of commitments. However, this model requires a longer delay between the commit and reveal phases, proportional to the UTXO value at stake.

For more comprehensive details on the proving and verifying processes involved in DropKick, please visit conduition.io/bitcoin/dropkick. Additionally, discussions within the Bitcoin Development Mailing List have highlighted that the effectiveness of DropKick relies on the prior establishment of a robust PQC system. The protocol itself cannot initially remedy systems delaying updates; it is usable only if there is an existing, reliable PQC infrastructure tailored for Bitcoin. This underlines the essential requirement of having foundational PQC solutions before implementing mechanisms like DropKick effectively at the user level.