How Tidecoin Compares to Bitcoin, QRL, and Others

Post-quantum cryptocurrency designs are not all trying to solve the same problem. Some protect transaction authorization from genesis. Some retrofit new output types into an existing chain. Some use post-quantum signatures for proofs or interoperability rather than ordinary user spends.

This page is a comparison guide, not a ranking. The protocol details for Tidecoin live in Protocol / Design Positioning.

Comparison Table

Project or approach	PQ scope	Signature model	Stateful signing	Main tradeoff
Tidecoin	Transaction signatures from genesis, PQHD, transport, script extensions	Falcon-512 live; Falcon-1024 and ML-DSA implemented behind activation	No	Larger transactions than ECDSA, but no historical ECDSA transaction-signing exposure
Bitcoin BIP 360 / P2MR	Proposed Bitcoin output type for long-exposure quantum resistance	Creates a script-tree output without Taproot key-path spend; PQ signatures are future work	Depends on future script choices	Conservative retrofit path, but not a complete PQ signature migration by itself
QRL	Chain built around XMSS hash-based signatures	XMSS / hypertree address scheme	Yes	Strong hash-based assumptions, but users and wallets must manage one-time signature state
Algorand state proofs	PQ proofs of Algorand history for light verification	Falcon state-proof signatures	No for state-proof users	Protects state proofs, not the same as making every ordinary account signature PQ
Classical ECDSA/Schnorr chains	No native PQ transaction authorization	ECDSA or Schnorr	No	Small signatures today, but needs future migration

Tidecoin

Tidecoin’s differentiator is scope. It is a Bitcoin-architecture chain whose mainnet transaction signatures have been post-quantum since genesis. The design also includes PQHD wallet derivation, post-quantum transport support, and activation-gated script/signature upgrades.

The cost is size and complexity: post-quantum keys and signatures are larger, and wallet/signing infrastructure must understand PQHD and scheme policy.

Bitcoin Retrofit Proposals

Bitcoin retrofit work has a different constraint: it must preserve a very large existing ecosystem. BIP 360 proposes Pay-to-Merkle-Root (P2MR), a draft soft-fork output type that removes Taproot’s key-path spend and creates a script-tree output resistant to long-exposure quantum attacks.

BIP 360 is important, but it is not the same thing as a complete Bitcoin post-quantum signature migration. The BIP itself frames post-quantum signatures as future work for short-exposure protection.

Primary source: bitcoin/bips bip-0360.mediawiki .

QRL

QRL uses XMSS, a hash-based signature approach. The advantage is conservative hash-based security assumptions. The operational tradeoff is statefulness: an OTS key index should be used only once, and reuse can compromise funds.

That is a real design difference. Tidecoin chose stateless lattice signatures so ordinary wallet usage does not depend on one-time-signature index discipline.

Primary sources: QRL address scheme and QRL OTS keys .

Algorand

Algorand uses Falcon in state proofs. That is a meaningful post-quantum feature: state proofs help light clients verify Algorand history with quantum-safe proof signatures.

It is also a different scope from Tidecoin. Algorand state proofs do not mean every ordinary user transaction signature is a Tidecoin-style PQ transaction signature from genesis.

Primary sources: Algorand state proofs and Algorand Falcon specification .

What To Compare

When evaluating a post-quantum chain or proposal, ask:

Are ordinary transaction signatures post-quantum?
Was the chain PQ from genesis or is it a retrofit?
Are signatures stateful or stateless?
What happens to old exposed public keys?
How large are public keys and signatures?
Is wallet derivation designed for post-quantum keys?
Is the work live, draft, testnet-only, or future roadmap?
What does the project cite as its primary specification?

Practical Takeaway

Tidecoin is best understood as a full-stack, Bitcoin-architecture PQ chain from genesis. Bitcoin retrofit proposals are constrained migration paths for the largest existing UTXO system. QRL is a hash-based, stateful-signature chain. Algorand uses Falcon for state proofs. These are different designs, not interchangeable labels.