[bitcoin-dev] Draft BIP for discussion: Time-Shifted Proof of Work (TSPOW) — an informational consensus-design proposal

[Jack Liao]

Hi all,

I am sharing a draft BIP for feedback before submitting it to the bips
repository. It is classified as Informational: it documents a consensus-design
pattern and its security analysis. It does NOT recommend activating a hard fork
on the Bitcoin main chain.

WHAT THE PROPOSAL IS

Time-Shifted Proof of Work (TSPOW) separates the three roles Bitcoin binds into
a single event — finding a hash below target, earning the block reward, and
authoring the block — into two stages:

1) Stage 1 (warrant issuance): miners produce a valid initial-hash warrant H_n
   (H(header, nonce) < D1), which carries the right to the new-coin reward.
   Rewards are deferred and warrants expire.

2) Stage 2 (selection): once k warrants accumulate (an adaptive Gamma batch),
   the protocol elects a block producer from the candidate pool via
   argmin H(h, R, PrevBlockHash), where R is an external-beacon output (with the
   previous block hash as the chain-derived fallback seed).

Two claimed properties, both backed by the whitepaper and by cross-checked
simulation (Rust / C++ / Python; see the repository):

- Block-time stability: the block interval becomes a Gamma(k, lambda) sum
  instead of a single exponential arrival, dividing block-time variance by 1/k.
- Withholding economics: warrant expiry plus deferred reward make privately
  mining / withholding a warrant strictly suboptimal (expected payoff strictly
  decreasing in delay).

WHAT THE PROPOSAL HONESTLY DOES NOT CHANGE

- A >50% adversary still dominates warrant generation and thus pool
  composition; 51%-attack security is unchanged natively.
- Without the external beacon, the long-run double-spend probability remains
  (q/p)^z, identical to traditional PoW.

KNOWN COSTS / RISKS (TO BE TRANSPARENT)

- External beacon = a new trust assumption. The election only fully eliminates
  private mining when an honest beacon is present; a compromised or censored
  beacon degenerates to the weaker chain-derived seed.
- Hard fork. Adopting TSPOW changes the block header, replaces direct block
  authorship with pool-based selection, and reallocates rewards. This is by
  construction a severe backward-incompatible change — another reason this is an
  informational document, not an activation proposal.
- Pool-flooding within a window is mitigated (chained FIFO, per-owner caps) but
  not eliminated; residual risk should be stress-tested.

MATERIALS

- BIP draft: bip-corepool-timeshiftpow (source in the repository below)
- Reference implementations, verification scripts, and numerical checks:
  https://github.com/corepool/timeshiftpow
- Whitepapers (CN + EN) and formal security analysis in the same repository.

I would welcome scrutiny of the Gamma block-time argument, the
withholding-economics model, and the beacon trust model in particular, both on
this list and in the BIP's security-considerations section.

Comments-Summary: No comments yet.

Thanks,
corepool

[Saint Wenhao]

> Hard fork.

I guess it could be turned into a no-fork, if you would just create a mining pool, working with your rules.

> changes the block header

If it is compatible, then it doesn't matter. For example: locally, each node could extract the difficulty out of the block header, and have a chain of difficulty periods, stored separately, and copy-pasted into the actual header, when needed. Then, every two weeks, instead of having "80 * 2016 bytes", it could be "4 + (76 * 2016) bytes", when it comes to the way it is stored locally. Will it change the header? Sure. Will it be backward-compatible? Of course.

> replaces direct block authorship with pool-based selection

Existing mining pools already did de-facto that. Miners are paid per shares, there are not that many solo miners anymore.

> and reallocates rewards

Again, in practice, miners create blocks, sending coins to the pool operator, and later, they are splitted, based on sent shares.

--
You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group.
To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/4bbb1017-8080-4916-8f85-082d2ebf5eacn%40googlegroups.com.

[Jack Liao]

Subject: Re: [bitcoin-dev] Draft BIP for discussion: Time-Shifted Proof of Work
Subject: Re: [bitcoin-dev] Draft BIP for discussion: Time-Shifted Proof of Work
(TSPOW) — an informational consensus-design proposal

Hi,

I appreciate the review and the decision on the bips repository. Rather than
re-litigating scope, I want to put the technical case on record, because I
believe TSPOW addresses flaws in the existing single-stage PoW model that have
been known for years but never fixed by a design that stays on one chain. There
are three structural improvements worth a serious look.

1. BLOCK-TIME STABILITY — fixing the variance.

Bitcoin binds "find a hash below target" and "author the block" into a single
event. The block interval is a single exponential arrival: mean = 1/lambda,
variance = 1/lambda^2, i.e. a unit coefficient of variation. Real PoW chains
inherit exactly that variance — blocks arrive in bursts and on occasion with
long gaps, which is the source of wide confirmation-latency variance and of
the persistent "lucky vs unlucky" mining outcomes.

TSPOW separates warrant issuance from block authorship and lets block
production wait for k *accumulated* warrants. The block interval then follows
a Gamma(k, lambda) distribution whose variance is divided by k (Section 3.1 of
the whitepaper; cross-checked in Rust, C++, and Python simulations in the
repo). With k = sqrt(S), even a modest pool gives a variance reduction of an
order of magnitude or more. This is an improvement to the chain's own
scheduling behaviour — no second chain, no peg, no bridge.

2. REMOVING THE SELFISH-MINING SURFACE.

In single-stage PoW a valid proof can be withheld and revealed later to force
a reorganization. Selfish mining uses exactly this: an adversary with < 50%
hash power can amplify its share of produced blocks by withholding, lowering
the effective security threshold of the network. This is a known, measured
weakness of the current model.

TSPOW makes withholding economically self-defeating: warrants expire (L) and
rewards are deferred, so holding a proof past its validity window yields
nothing. And because the elected producer is chosen by
argmin H(h, R, PrevBlockHash) over an immutable chained pool, a withheld proof
can no longer be inserted to rewrite the pool state. The design removes the
amplification vector rather than patching around it.

3. DECENTRALIZING WHO PRODUCES BLOCKS.

In single-stage PoW, the fastest hash wins, which structurally rewards the
largest pools and concentrates eventual authorship in a few entities. TSPOW
decouples "who did the work" from "who writes the block":

- warrants (who earned the subsidy) are created by proof of work;
- authorship (who writes the block and earns fees) is elected by argmin over
the mature pool, seeded by an external randomness beacon R with the previous
block hash as the chain-derived fallback.

The producer-staking, challenge-window, and deferred-fee mechanics are aimed
directly at incentive collusion among block producers, reducing the
centralizing
pull of the largest mining entities without creating a separate network.

WHY I FILE THIS AS INFORMATIONAL

The Informational label reflects a maturity posture — this is a
research proposal
with a formalized spec and security analysis, not a recommendation to
activate on
Bitcoin today. I understand the bips repository's scope policy is targeted at
adoption proposals, and I accept that as a policy decision. The
technical point I
want on the public record is simply that TSPOW is an in-chain,
consensus-authoring
modification with three concrete improvements over the existing PoW model:
Gamma-scheduled, low-variance block times; elimination of the withholding /
selfish-mining amplification; and a more decentralizing separation of work from
authorship.

Full spec, whitepaper, security analysis, and cross-checked simulations:
https://github.com/corepool/timeshiftpow

Thanks for reading.

--
BR.
Jack.