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H5 — High input count (CIOH)

Severity: Warning · Weight: 10 · Network: No

What it detects

The transaction has 5 or more inputs. This triggers the Common Input Ownership Heuristic (CIOH): an analyst may assume all inputs are controlled by the same wallet.

Why it matters

Consolidating many inputs in a single transaction is a common pattern that reveals wallet structure. It effectively announces "these UTXOs all belong to the same entity."

H9/H10 suppression

When H9 or H10 fires (coinjoin input or coinjoin transaction detected), H5 is automatically suppressed. Coinjoin transactions intentionally have many inputs from different wallets — applying CIOH would be a false positive.

What to do

  • Limit consolidation to 2–4 inputs per transaction
  • Consider using a coinjoin to merge UTXOs without revealing common ownership
  • If you must consolidate many inputs, do it in a dedicated consolidation transaction when fees are low, rather than combining it with a payment