Cryptoasset Anti-Financial Crime Specialist (CCAS) Certification Practice Test

What is the heuristic to cluster input addresses in a Bitcoin transaction with multiple inputs and one recipient?

1. Change

2. Common spend

3. Merkle tree

4. Input/output

The correct answer is: Common spend

In the context of Bitcoin transactions, especially those that involve multiple inputs and a single recipient, the heuristic to cluster input addresses is referred to as "Common spend." This technique is based on the observation that when multiple inputs are included in a transaction, there is a high likelihood that they are controlled by the same entity. This is because it is common practice for users to consolidate their funds from several addresses into one transaction to minimize transaction fees or when making a payment. By grouping these inputs together as common spend, analysts can deduce that the addresses controlling those inputs are likely linked or belong to the same user. This clustering result can be extremely valuable in analyzing transaction patterns and uncovering the underlying relationships among different Bitcoin addresses. It plays a critical role in anti-money laundering (AML) efforts, as well as investigations into the flow of funds and identification of potential illicit activity. The other concepts listed do not serve this specific clustering purpose. "Change" refers to the remaining amount of Bitcoin sent back to the sender's wallet after the transaction is processed, but does not relate to identifying linked inputs. "Merkle tree" is a structure used in blockchain to efficiently and securely verify data, but it does not cluster inputs in a transaction. "Input/output" refers