OP_CIV - Post-Quantum Signature Aggregation

The conversation highlights the challenges and implications of implementing OP_CIV within wallet development, emphasizing the technical difficulties that arise from the need to statefully track prior UTXOs and generate addresses based on a changing UTXO set over time. This complexity is contrasted with the current practices of some wallet developers who do not support multi-address functionality, indicating a significant shift in requirements for those considering the adoption of OP_CIV.

Furthermore, the discussion delves into the privacy advantages offered by employing CoinSwap Indistinguishable Address (CISA) techniques over address reuse. When two payments are received at distinct addresses that are linked via OP_CIV or similar methods, it provides the user with the discretion to reveal the common ownership of those UTXOs. This approach offers enhanced privacy compared to receiving multiple payments at a single address, which directly reveals ownership. The flexibility in revealing UTXO ownership is particularly valuable given that users typically manage multiple UTXOs, allowing for more strategic control over on-chain privacy. This is set against the backdrop of existing chainalysis techniques, which rely on common-input ownership heuristics, despite their potential inaccuracies.

The email also quantifies the additional costs associated with executing transactions under the CISA paradigm. It outlines the witness size increase per additional input covered by CISA, providing a formula to calculate the extra bytes required in the witness data. For instance, using a taptree of height h results in a specific calculation for the additional witness bytes needed ((n - 1)((h + 1) * 32)), illustrating the scalability of witness size based on the number of inputs and the height of the taptree. With a taptree of height 8, accommodating up to 255 CISA commitments, the cost in terms of witness bytes per additional input is clarified, offering a concrete perspective on the resource implications of adopting such privacy-enhancing techniques in blockchain transactions.