Public-Key-Exposed Supply

What is it?

A Bitcoin signature rests on elliptic curves. As long as only the hash of a public key sits on-chain, that key is out of reach. The moment it appears in the clear, it becomes a theoretical entry point for a sufficiently powerful quantum machine, which could derive the private key from it. This chart stacks the BTC held by addresses that have already exposed their public key, script type by script type. The criterion is twofold: the key must have appeared on-chain, AND the address must still hold a balance. An emptied address has nothing left to lose and does not count. Exposure follows two clearly distinct paths: • **Structural** - P2PK and P2TR write the public key into the output itself. These BTC are exposed from the moment they are funded, without the holder doing anything. For P2PK, this is the original mining format of 2009-2010. For P2TR (Taproot), it is the 32-byte x-only key encoded in the bc1p address. • **Behavioural** - P2PKH, P2SH, P2WPKH and P2WSH publish only a hash. The full key appears only when spending, written into the witness or the scriptSig. These types therefore count only for the fraction that has already spent and still holds something: this is the very definition of address reuse. The sum of the bands gives exposed supply, not total supply. The rest of the supply lives in addresses that have never spent and whose hash alone is public.

How to read

Each layer is one script type, in absolute BTC. The total thickness of the stack is exposed supply on a given date. Read the stack as two blocks rather than seven layers: 1. **The two P2PK bands and the P2TR band** form structural exposure. They always equal 100 % of their respective type, since these formats expose by construction. 2. **The four hashed bands** form behavioural exposure. Each represents only a fraction of its type: the rest of that type has never spent. Comparing the two blocks is the main reading. The behavioural block weighs considerably more than the structural one, which shifts the question from « the old coins of 2009 » to « today's spending habits ». A band growing does not mean coins have been stolen. It means a larger quantity of BTC now rests on a public key that is visible.

Key zones

• **A near-motionless P2PK band** - these coins have not moved since the network's earliest years. The band is flat because nothing enters or leaves it. Any notable variation would be a historic event in itself. • **A P2TR band that does not exist before late 2021** - Taproot activated in November 2021. Before that date the band is absent, which is correct and not a data gap. Since then it grows with adoption, and every BTC entering it mechanically adds structural exposure. • **Hashed bands at variable fractions** - depending on the type, between a quarter and close to half of the type has already spent while keeping a balance. P2WSH shows the highest fraction, consistent with script usage involving repeated movement. P2WPKH shows the lowest in proportion but weighs most in absolute volume, simply because it is the most widely held format. • **The total relative to supply** - is read on the « Public-Key-Exposed Supply Share » chart, which is the same measurement expressed as a percentage.

What to observe

Three movements deserve attention. **A hashed band thickening** indicates that more BTC rest on addresses that have already spent. This is a change in practice, not in protocol: every wallet reusing an address instead of deriving a fresh one feeds that band. **The P2TR band growing** adds structural exposure through adoption alone. This is the Taproot paradox: the network's most modern format is also the one that exposes its public key from the first satoshi received. In exchange, a post-quantum signature scheme would graft onto it more easily. **A shrinking P2PK band** would mean coins from the 2009-2010 era are moving again. That would be the heaviest reading this chart could offer, and it has never happened at meaningful scale. Cross-reference with « Supply by Protocol Type »: that chart shows full supply by type, this one shows only the exposed fraction. The gap between the two, type by type, is exactly the share protected by a hash.

Historical context

The history of exposure follows that of address formats. In 2009 and 2010, mining paid out in P2PK: the public key was written in the clear in every coinbase output. Nearly all of the supply at the time was therefore exposed by construction. P2PKH, which publishes only a hash, took over next and pushed the exposed share down for more than a decade. P2SH in 2012 and then SegWit in August 2017 extended that movement: each new format published a hash rather than a key. The activation of Taproot in November 2021 reversed that logic. For the first time since the origin, a widely adopted format writes the public key back into the output. Combined with address reuse that is not receding, this shift explains why the exposed share turned back up after reaching its low in the early 2020s.

Expert notes

**The exact predicate.** An address counts if its public key or spending script has appeared on-chain, and if it still holds a balance at the block considered. P2PK and P2TR satisfy the first condition from funding, hashed types only after a spend. This twofold criterion is what separates this measurement from a plain count of reused addresses: an address that has received many times without ever spending exposes nothing. **Two limits worth knowing.** Bare multisig (P2MS) writes its public keys in the clear and should therefore appear here, but it lives outside the address model: no band represents it. The stake amounts to tens of BTC against a supply of twenty million, a negligible order of magnitude for reading the chart. We state it rather than omit it. The 65-byte P2PK band shows an exposed balance very slightly above its own type's supply. The gap is exactly 150 BTC, three times the block subsidy of the era, and it settles in three steps: 50 BTC from January 2009, 100 on 14 November 2010, 150 the day after. These are three mining rewards whose public key sits on the chain but which the UTXO set does not contain: the genesis block coinbase, which the reference implementation never adds to it, and two duplicate coinbases from November 2010 that overwrote earlier identical ones. Those three outputs are therefore exposed without being part of supply. **Going further.** The ratio between the behavioural block and the structural block is an indicator of practice, not of protocol. It rises when habits degrade and falls when wallets systematically derive fresh addresses. It is the only one of the two blocks over which an individual holder has any hold.

Common mistakes to avoid

**Mistake 1: confusing exposed with compromised.** This chart measures a theoretical attack surface, not a loss. No publicly known machine breaks the elliptic curves Bitcoin uses. An exposed BTC remains a held BTC. **Mistake 2: assuming these are Satoshi-era coins.** This is the most widespread intuition and the chart contradicts it directly: the behavioural block, arising from address reuse by present-day holders, weighs more than the entire structural block combined. **Mistake 3: assuming any address that received several times is exposed.** Receiving reveals nothing. Only a spend writes the public key on-chain. An address funded a hundred times and never spent appears in no band. **Mistake 4: reading Taproot as a regression.** Taproot re-exposes the public key, that is a fact, and the chart shows it. But its signature scheme lends itself better to migrating towards a quantum-resistant algorithm. The chart measures the present state, not the ease of the exit. **Mistake 5: adding this stack to « Supply by Protocol Type ».** The two charts describe the same BTC from two angles. This one is a subset of the other, not a complement.

Programmatic access

REST API

curl -sS \
  'https://api.trinityinsights.io/api/v1/onchain/metrics/quantum-exposed-supply/data?timeframe=90d' \
  -H 'X-API-Key: $TRINITY_API_KEY'

MCP server

{
  "tool": "get_chart_value",
  "metric_id": "quantum-exposed-supply",
  "timeframe": "1y"
}

Required tier: pro. See the pricing grid for the tier list and the MCP documentation for multi-client configuration.

Related metrics

• quantum-exposure-share
• supply-by-protocol-type
• script-type-distribution
• taproot-adoption

Institutional disclaimer

Trinity Insights is an educational and analytical tool. The metric above does not constitute investment advice. Trinity Insights is not a Crypto-Asset Service Provider (CASP) registered under MiCA Regulation (EU) 2023/1114. See the full disclaimer.