Assentian-PQE (SNTI) Whitepaper

1 Abstract

Assentian-PQE (SNTI) is the world's first mineable blockchain secured by post-quantum cryptography. Built on a fork of Bitcoin Core v27, SNTI replaces ECDSA with XMSS (Extended Merkle Signature Scheme) — a hash-based signature scheme standardized in NIST SP 800-208 that is resistant to attacks from both classical and quantum computers.

Unlike existing "quantum-resistant" projects that are either non-mineable, use unproven cryptographic assumptions, or are centralized, SNTI delivers a fully decentralized, proof-of-work blockchain with mathematically proven quantum resistance — while maintaining the battle-tested architecture of Bitcoin.

2 The Quantum Threat

2.1 — Shor's Algorithm

In 1994, Peter Shor published a quantum algorithm that can efficiently solve the discrete logarithm problem and integer factorization — the mathematical foundations of ECDSA, RSA, and all widely-used digital signatures. A sufficiently powerful quantum computer running Shor's algorithm can derive private keys from public keys in polynomial time.

2.2 — Current Blockchain Vulnerability

Bitcoin, Ethereum, and virtually all existing blockchains rely on ECDSA (Elliptic Curve Digital Signature Algorithm). When a quantum computer with ~1,500+ logical qubits becomes available, ECDSA-256 will be broken. Current estimates suggest this could happen within 10-20 years.

2.3 — "Harvest Now, Decrypt Later"

Adversaries are already harvesting public keys from blockchain transactions today, planning to decrypt them when quantum computers become available. This means funds in exposed addresses are already at risk — even before quantum computers exist.

3 Our Solution

Assentian-PQE (SNTI) addresses the quantum threat with a two-pronged approach:

1. XMSS Signatures (Primary): Hash-based signatures with mathematical proofs of quantum resistance. No known quantum algorithm provides any significant speedup against hash-based cryptography.
2. ECDSA (Supplementary): Maintained for backward compatibility during the transition period. Users can choose their security level.

3.1 — Why XMSS?

• NIST Standardized: SP 800-208 (2020) — approved for government use
• Minimal Assumptions: Security relies only on hash function properties
• Proven Security: 15+ years of cryptanalysis with no significant weaknesses found
• No Quantum Speedup: Grover's algorithm provides at most √N speedup — easily mitigated by increasing hash output size

3.2 — Hybrid Architecture

Assentian-PQE (SNTI) uses a hybrid approach where both ECDSA and XMSS transactions coexist on the same chain. The script engine distinguishes signature types by key size:

4 Technical Architecture

4.1 — Base Layer: Bitcoin Core v27

Assentian-PQE (SNTI) is built on Bitcoin Core v27 — the most battle-tested blockchain codebase in existence. This provides:

• Proven UTXO model and transaction validation
• Mature P2P networking stack
• Robust mempool and block propagation
• Extensive RPC API and tooling
• Active security maintenance and updates

4.2 — Consensus Parameters

4.3 — Script Extensions

Assentian-PQE (SNTI) extends Bitcoin Script with a new opcode:

OP_XMSS_CHECKSIG = 0xBB

This opcode verifies a 64-byte XMSS public key against a ~2500-byte XMSS signature. The verification follows the XMSS specification in RFC 8391 / NIST SP 800-208.

5 XMSS Deep Dive

5.1 — How XMSS Works

XMSS (Extended Merkle Signature Scheme) is a stateful hash-based signature scheme built on four cryptographic primitives:

1. WOTS+ (Winternitz One-Time Signature): Signs individual message chunks
2. Merkle Tree: Aggregates 2^h WOTS+ public keys into a single root (the XMSS public key)
3. BDS Algorithm: Efficiently updates the Merkle tree after each signature
4. Leaf Index: Tracks which WOTS+ key is used next (stateful)

5.2 — SNTI XMSS Parameters

5.3 — Stateful Key Management

XMSS is a stateful signature scheme — each signature consumes one leaf of the Merkle tree, and the leaf index must be tracked and persisted. SNTI handles this through:

• Automatic leaf index tracking in the wallet keystore
• Atomic state updates after each signature
• Encrypted state persistence on disk
• Recovery mechanisms for state synchronization

6 Security Analysis

6.1 — Quantum Resistance Proof

XMSS security against quantum adversaries:

• Shor's Algorithm: Does not apply to hash-based signatures. No known quantum algorithm breaks preimage resistance of cryptographic hash functions.
• Grover's Algorithm: Provides at most √N speedup for preimage search. With SHA-256 (n=256), quantum preimage resistance is 2^128 — still computationally infeasible.
• Collision Resistance: Quantum birthday attacks reduce collision resistance from 2^128 to 2^85. Still far beyond practical reach.

6.2 — Known Limitations (Honest Disclosure)

• Stateful: Key state must be carefully managed. Lost state = potential key reuse.
• Limited Signatures: Each key can only sign 2^10 = 1,024 messages. New keys must be generated after exhaustion.
• Larger Signatures: ~2,500 bytes vs ~72 bytes for ECDSA. Increases transaction size and block space usage.
• Not Post-Quantum PoW: SHA-256 PoW is quantum-resistant enough (Grover's gives only 2x speedup), but mining is not "post-quantum" in the same sense as signatures.

6.3 — Comparison with Alternatives

7 Token Economics

7.1 — Supply Schedule

7.2 — Fee Market

Transaction fees follow Bitcoin's model: users bid for block space. As block rewards decrease over time, fees become the primary miner incentive. The 60-second block time provides faster confirmation while maintaining reasonable orphan rates.

7.3 — Mining

• Algorithm: SHA-256 (same as Bitcoin)
• Hardware: ASIC miners (SHA-256 compatible)
• Block Signing: Miners sign found blocks with XMSS (proving quantum-resistant block production)
• Pools: Compatible with existing Stratum protocol mining pools

8 Roadmap

Future Research

• PoUW v2: Proof of Useful Work — integrating LLM inference as an alternative to hash-based mining
• XMSS^MT: Multi-tree XMSS for unlimited signatures per key
• SPHINCS+ Support: Stateless hash-based signatures as an alternative option
• Lightning Network: Layer-2 payment channels with XMSS-signed channels

9 References

1. NIST SP 800-208 — "Recommendation for Stateful Hash-Based Signature Schemes" (2020)
2. RFC 8391 — "XMSS: Extended Merkle Signature Scheme" (2018)
3. Shor, P. — "Algorithms for Quantum Computation" (1994)
4. Grover, L. — "A Fast Quantum Mechanical Algorithm for Database Search" (1996)
5. Bitcoin Core v27 — github.com/bitcoin/bitcoin
6. NIST PQC Standardization — csrc.nist.gov/projects/post-quantum-cryptography
7. Bernstein, D.J. & Lange, T. — "Post-Quantum Cryptography" (2017)