Tidecoin

Is Tidecoin quantum-safe?

Where we are making a judgement call Tidecoin ranks outside the seventy-five largest layer 1s and is covered on the deployment test, because a post-quantum signature runs on its mainnet. We confirmed the chain was live on 23 October 2026, when its explorer reported block 2,784,870 at 05:30 UTC. Two judgement calls shape the row. First, NIST alignment is a 7 rather than the 8 a deployed NIST selection would otherwise get, because Tidecoin's whitepaper says mainnet verifies Falcon under a relaxed legacy acceptance bound rather than the specified one; reading the scheme as plain Falcon-512 would give 8 and a Hardy Score of 90.5 rather than 89.0. Second, verification is a 5 on the view that a NIST mailing-list discussion is not review of the implementation; counting it as public review would give 6 and a Hardy Score of 89.5. The released node is v0.18.3 from 2022, and the 1.0 line is still at release candidate. We did not compile or run the node: the signature finding rests on the released source and on transactions read through the public explorer. The upcoming AuxPoW activation moves mining to merged mining with Litecoin, which would not take Tidecoin outside its own consensus.

At a glance

Cryptography in use

• Account signatures FN-DSA Falcon-512 (round 3, PQClean) Mainnet, mandatory Every input in the sampled transaction carries an 898-byte key (897-byte Falcon-512 key plus prefix) and a 655 to 663-byte signature. The v0.18.3 verifier calls Falcon-512 alone. Read on-chain
• Account signatures FN-DSA Falcon-1024 Specified, not deployed In the 1.0 release candidates, gated on the AuxPoW activation, which is disabled in the mainnet parameters. Source code or release
• Account signatures ML-DSA ML-DSA-44, ML-DSA-65, ML-DSA-87 Specified, not deployed In the 1.0 release candidates, gated on the same activation. Source code or release

A role not listed is not evidenced either way. Every scheme, and which other chains share it, is in the cryptography registry.

Score breakdown

How it compares

Roadmap

1. 27 December 2020 shipped

   Tidecoin's genesis block is mined, with Falcon-512 in place of ECDSA as the signature for every spend. source

2. 2 March 2022 shipped

   Tidecoin Core v0.18.3 is released, with binaries for Linux, macOS and Windows. It is the current final release, and its verifier calls Falcon-512 alone. source

3. 20 October 2026 in-progress

   Tidecoin v1.0.0rc2 is published as a release candidate, built on a codebase initially based on Bitcoin Core v30 and carrying Falcon-1024, ML-DSA-44, 65 and 87, strict Falcon verification and ML-KEM-512 peer transport, all gated on the AuxPoW activation. source

4. No date published planned

   AuxPoW activation, the single height-gated upgrade that switches mining to scrypt merged mining with Litecoin and turns on the further signature schemes. The mainnet parameters set it to disabled, and no activation height has been published. source

If holders never migrate

Not applicable

Every Tidecoin output since the genesis block has been protected by Falcon-512, so there are no classical-key coins to migrate.

As of 23 October 2026. Published beside the score, not in it. Every chain's stance is compared on the commitments page.

Exposure

Exposure measures how much of the chain's value already sits behind a public key that an attacker can record today and break later. This is the part of the threat that a future upgrade cannot undo.

Tidecoin keeps Bitcoin's output model, so a public key appears on-chain when the output it protects is spent, and addresses before that are hashes. The difference is what that key is. Every Tidecoin key since genesis has been a Falcon-512 key, and recording one today gives a future quantum computer nothing Shor's algorithm can use, so the harvest-now-decrypt-later exposure this dimension exists to measure does not arise. Tidecoin is not a fork of another chain's history: it has its own genesis block, so it inherits no classical outputs. What a holder is relying on instead is that Falcon-512 holds up, in the round 3 form and the relaxed legacy verification mode mainnet uses today.

Questions

Sources

1. Tidecoin repository and README Tidecoin · primary · checked 23 October 2026
2. Tidecoin Core v0.18.3: src/pubkey.cpp Tidecoin · primary · checked 23 October 2026
3. Tidecoin Core v0.18.3: src/pubkey.h Tidecoin · primary · checked 23 October 2026
4. Tidecoin Core v0.18.3 release Tidecoin · primary · checked 23 October 2026
5. Tidecoin v1.0.0rc2 release candidate Tidecoin · primary · checked 23 October 2026
6. Tidecoin whitepaper Tidecoin · primary · checked 23 October 2026
7. Tidecoin chain parameters: src/kernel/chainparams.cpp Tidecoin · primary · checked 23 October 2026
8. Tidecoin Block Explorer: transaction 84952925...d30d04919 Tidecoin Block Explorer · primary · checked 23 October 2026
9. Post-Quantum Cryptography project NIST · primary · checked 23 October 2026
10. Falcon: Fast-Fourier Lattice-based Compact Signatures over NTRU Falcon team · primary · checked 23 October 2026

@misc{hardyindex_tidecoin_2026,
  author       = {{The Hardy Index}},
  title        = {Tidecoin: quantum readiness assessment},
  year         = {2026},
  howpublished = {\url{https://hardyindex.com/chains/tidecoin}},
  note         = {Hardy Score 89.0 of 100, Tier 1: Native. Methodology v1.8},
  urldate      = {2026-11-13}
}