Bitcoin Shared Send Transactions Untangling in Numbers

Abstract

Bitcoin uses an unspent transaction output (UTXO) model for coin circulation, which is similar to the banknotes. The transaction history is publicly available and allows to trace cryptocurrency flows. Different users merge transactions into a single bigger one to tangle flows. The merged transaction is called a shared send mixer (SSM). One can try to find the original subtransactions–solve an untangling problem. Based on the number of untanglings and their size, one extracts additional information about coin circulation. Theoretical analysis of the untangling problem is known from the literature. The paper aims to collect statistics of the SSM usage by transaction type for Bitcoin blockchain. We propose an algorithm to solve the problem, prove its correctness, and provide a source code. We applied the algorithm to the Bitcoin historical data. 15% transactions are SSM, and 90% of them allow unique untangling. The future work is an algorithm application to other UTXO systems and the results adaptation to an address grouping.