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.

// full-stack pq

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

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

Layer	Bitcoin	Tidecoin	NIST Standard	Status
Transaction signing	ECDSA (secp256k1)	FALCON-512 (default since genesis)	Draft FIPS 206	Live
Additional signatures	—	Falcon-1024, ML-DSA-44/65/87	FIPS 204, Draft FIPS 206	Built
P2P transport encryption	ECDH-based key exchange	ML-KEM-512	FIPS 203	Live
Witness script hashing	SHA-256 (128-bit PQ security)	SHA-512 (256-bit PQ security)	FIPS 180-4	Built
HD wallet derivation	BIP-32 (ECDSA xpub)	PQHD (hardened-only, SHA-512 KDF)	Custom	Live
Proof-of-work (Phase 1)	SHA-256d	powerTIDE (memory-hard, CPU)	—	Live
Proof-of-work (Phase 2)	—	Scrypt via Litecoin merged mining	—	Built

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

// falcon-512

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.

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

Deep dive into FALCON-512

Parameter	FALCON-512	ECDSA (Bitcoin)
Public key	897 B	33 B
Signature	666 B	71 B
PK + Sig	1,563 B	104 B
Classical security	2^113+ (lattice reduction)	2^128 (Pollard's rho)
Quantum security	Secure (no known algorithm)	Broken (Shor's algorithm)
Verification speed	~28,000/s	~10,000/s

// 5 signature schemes

What post-quantum signature schemes does Tidecoin support?

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

Scheme	Prefix	PK	Signature	NIST Level	Standard	Status
Falcon-512	0x07	897 B	666 B	1 (~AES-128)	Draft FIPS 206	Live
Falcon-1024	0x08	1,793 B	1,280 B	5 (~AES-256)	Draft FIPS 206	Built
ML-DSA-44	0x09	1,312 B	2,420 B	2 (~AES-128)	FIPS 204	Built
ML-DSA-65	0x0A	1,952 B	3,309 B	3 (~AES-192)	FIPS 204	Built
ML-DSA-87	0x0B	2,592 B	4,627 B	5 (~AES-256)	FIPS 204	Built

// ml-kem-512 transport

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).

// pqhd wallet

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.

Full PQHD technical explanation

// script extensions

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.

// auxpow merged mining

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.

// 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.