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Tidecoin Post-Quantum Technology

Every cryptographic layer — signatures, transport, wallet, mining — uses algorithms designed to resist quantum computers. Not planned. Not proposed. Live since 2020.

What does "full-stack post-quantum" mean?

Unlike projects that add quantum resistance at only one layer, Tidecoin secures every cryptographic surface:

LayerTidecoin (Post-Quantum)Bitcoin (Classical)NIST StandardStatus
Transaction signingFALCON-512 (default since genesis)ECDSA (secp256k1)Draft FIPS 206Live
Additional signaturesFalcon-1024, ML-DSA-44/65/87—FIPS 204, Draft FIPS 206Built
P2P transport encryptionML-KEM-512ECDH-based key exchangeFIPS 203Live
Witness script hashingSHA-512 (256-bit PQ security)SHA-256 (128-bit PQ security)FIPS 180-4Built
HD wallet derivationPQHD (hardened-only, SHA-512 KDF)BIP-32 (ECDSA xpub)CustomLive
Proof-of-work (Phase 1)YespowerTIDE (memory-hard, CPU)SHA-256d—Live
Proof-of-work (Phase 2)Scrypt via Litecoin merged mining——Built

Swipe to compare all columns

"Live" = active on mainnet today. "Built" = implemented, tested, activates with AuxPoW consensus upgrade.

What is FALCON-512 and why does Tidecoin use it?

FALCON-512 (Fast-Fourier Lattice-based Compact Signatures over NTRU) is a digital signature scheme selected by NIST in the Post-Quantum Cryptography competition and being standardized as FN-DSA under Draft FIPS 206. Tidecoin has used FALCON-512 as its primary signature scheme since genesis in December 2020 — to our knowledge, one of the earliest production deployments of this NIST-selected algorithm.

Why FALCON-512?

  • Smallest signatures of any NIST PQC lattice standard: 666 bytes (vs 2,420+ for ML-DSA)
  • Proven security in the Quantum Random Oracle Model under the SIS problem over NTRU lattices — studied since 1996 [Hoffstein, Pipher, Silverman, 1998]
  • Constant-time implementation using integer emulation (no native floating-point). Eliminates side-channel attacks like FALCON DOWN [2021] and SHIFT SNARE [2025]
  • Stateless — unlimited signatures per key, unlike XMSS which limits key reuse
ParameterFALCON-512ECDSA (Bitcoin)
Public key897 bytes33 bytes
Signature666 bytes71 bytes
PK + Sig combined1,563 bytes104 bytes
Classical security2^113+ (lattice reduction)2^128 (Pollard's rho)
Quantum securitySecure (no known algorithm)Broken (Shor's algorithm)
Verification speed~28,000 ver/s~10,000 ver/s

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Deep dive into FALCON-512

What post-quantum signature schemes does Tidecoin support?

Tidecoin implements five signature schemes from NIST's PQC standardization process (ML-DSA finalized as FIPS 204; Falcon in draft as FIPS 206), registered in a compile-time scheme registry with unique prefix bytes:

SchemePrefixPublic KeySignatureNIST LevelStandardStatus
Falcon-5120x07897 B666 B1 (~AES-128)Draft FIPS 206Live
Falcon-10240x081,793 B1,280 B5 (~AES-256)Draft FIPS 206Built
ML-DSA-440x091,312 B2,420 B2 (~AES-128)FIPS 204Built
ML-DSA-650x0A1,952 B3,309 B3 (~AES-192)FIPS 204Built
ML-DSA-870x0B2,592 B4,627 B5 (~AES-256)FIPS 204Built

Why multi-scheme?

Cryptographic agility. If a vulnerability is discovered in one lattice construction, Tidecoin can switch to an alternative scheme through a consensus upgrade — no hard fork, no emergency. This is defense-in-depth applied to algorithm selection.

ML-DSA complements Falcon with important advantages: no floating-point arithmetic at all, no Gaussian sampling, hedged signing by default, and FIPS 204 is already finalized (August 2024). The trade-off is larger signatures (2,420-4,627 bytes vs 666-1,280 bytes).

How does Tidecoin protect peer-to-peer communication?

Tidecoin's V2 transport protocol uses ML-KEM-512 (NIST FIPS 203) for post-quantum key encapsulation, replacing Bitcoin's ECDH-based key exchange. This is enabled by default (-v2transport=1).

ParameterSize
Public key800 bytes
Ciphertext768 bytes
Shared secret32 bytes

Why does P2P encryption matter for quantum resistance?

In a classical setting, P2P encryption prevents passive eavesdropping but is less critical because transactions are broadcast publicly. In a post-quantum setting, ML-KEM-512 prevents a quantum adversary from:

  • Intercepting transactions between broadcast and confirmation
  • Extracting public keys from unconfirmed transactions in the mempool
  • Correlating network metadata with quantum key-recovery attacks

What is the PQHD wallet?

PQHD (Post-Quantum Hierarchical Deterministic) is Tidecoin's custom wallet key derivation system. It replaces Bitcoin's BIP-32, which is broken by quantum computers — Shor's algorithm can derive the private key from any BIP-32 extended public key (xpub), making an exposed xpub equivalent to an exposed xpriv.

  • Hardened-only derivation

    No public key derivation (inherently unsafe for lattice schemes)

  • SHA-512 KDF

    For deterministic key generation

  • Multi-seed, multi-scheme

    Independent seeds with per-seed scheme policies

  • Encrypted storage

    Seeds encrypted with wallet master key

Derivation path:

m / 10007' / 6868' / scheme' / account' / change' / index'
Full PQHD technical explanation

What script extensions does Tidecoin add for quantum security?

  • OP_SHA512 (opcode 0xb3)

    Computes the SHA-512 hash of the top stack element. Under Grover's algorithm, SHA-256 provides 128-bit post-quantum security (NIST Category 1). SHA-512 provides 256-bit post-quantum security (NIST Category 5) — the maximum security margin.

  • Witness v1 with 512-bit script hash (P2WSH-512)

    Uses a 64-byte SHA-512 hash of the witness script instead of Bitcoin's 32-byte SHA-256 hash. PQ-native address format: q1... (mainnet), tq1... (testnet).

Both features are implemented and tested, gated behind AuxPoW activation consensus flags.

How will Tidecoin achieve long-term network security?

At a predetermined consensus height, Tidecoin activates Auxiliary Proof-of-Work (AuxPoW) for scrypt-based merged mining with Litecoin. This is not just a PoW change — it simultaneously enables all Phase 2 features.

Why merged mining?

  • A small standalone CPU-mined chain has a lower security ceiling than a large established mining base
  • Merged mining with Litecoin materially increases Tidecoin's inherited proof-of-work security
  • Litecoin miners can opt in voluntarily because Tidecoin block rewards provide additional revenue at negligible extra cost
  • The Dogecoin/Litecoin precedent shows how merged mining can dramatically strengthen a smaller chain's security model

Why scrypt is quantum-resistant:

  • Scrypt requires ~1.2 billion physical qubits for quantum attack including 128 KB QRAM in superposition — approximately 200x more than SHA-256d's ~2.4-10 million qubits
  • The QRAM technology required does not exist and faces fundamental physical scaling challenges
  • Scrypt is proven maximally memory-hard [Alwen et al., EUROCRYPT 2017, Best Paper]

All AuxPoW code is implemented and tested — chain ID 8, createauxblock/submitauxblock RPCs, scrypt parent PoW validation. Currently AUXPOW_DISABLED on mainnet, active at block 1000 on testnet.

How does Tidecoin mining work?

Tidecoin uses YespowerTIDE (N=2048, r=8), a memory-hard proof-of-work algorithm from the yespower/yescrypt family by Solar Designer. It is designed for CPU mining fairness:

  • Memory-hard

    Requires 1-16 MB RAM per hash

  • CPU-friendly

    Optimized for L2 cache access patterns

  • GPU-unfriendly

    Memory access patterns map poorly to GPU architectures

  • No premine

    All coins earned through proof-of-work from block zero

Tidecoin is designed for broad CPU participation rather than specialized-hardware dependence.

// technology faq

Technology FAQ

All FAQ

Is FALCON the same as NIST's FN-DSA?

Yes. FALCON (Fast Fourier Lattice-based Compact Signatures over NTRU) is the algorithm selected by NIST and being standardized as FN-DSA under Draft FIPS 206. To our knowledge, Tidecoin is one of the earliest production blockchains using FALCON-512 for all transaction signing, active since genesis (December 2020).

How does FALCON-512 compare to XMSS used by QRL?

FALCON-512 produces 666-byte stateless signatures — keys can sign unlimited messages. XMSS produces ~2,500-byte stateful signatures with limited key reuse (2^13 signatures per key tree). FALCON is a NIST Draft FIPS 206 standard; XMSS is defined in RFC 8391 but was not selected by NIST's PQC competition.

What happens if FALCON-512 is broken?

Tidecoin has four additional signature schemes from NIST's PQC process (Falcon-1024, ML-DSA-44/65/87) already implemented and tested. If a vulnerability is found in one construction, alternative schemes can be activated via consensus upgrade.

Does Tidecoin have ECDSA anywhere?

No. All classical cryptography — ECDSA, Schnorr, x-only pubkeys, Taproot/MuSig, and secp256k1 key derivation — was completely removed. No ECDSA exists anywhere in the protocol.

What does "Built" status mean?

"Built" means the feature is fully implemented in the source code, compiled, and tested (unit tests + functional tests), but not yet activated on mainnet. Activation occurs at a predetermined block height via the AuxPoW consensus upgrade. All "Built" features are active on testnet.

References