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1. Introduction

1.1 The Quantum Threat​

Virtually all existing blockchains rely on elliptic curve cryptography (ECC): secp256k1 (Bitcoin, Ethereum), Curve25519 (Solana, Cardano). Shor's algorithm solves the discrete logarithm problem in polynomial time on a quantum computer, rendering ECDSA and Ed25519 completely insecure. Even before fault-tolerant quantum computers, "harvest now, decrypt later" attacks mean that sensitive transaction data encrypted today may be decrypted retroactively once quantum capabilities arrive.

1.2 Why Retrofitting Fails​

  1. Soft-forking requires overwhelming consensus and invalidates all existing infrastructure.
  2. Address migration fails to protect transaction history and smart contract state.
  3. Hybrid signatures are recommended by ANSSI and other national agencies during the transition phase, but they double overhead and the classical component remains vulnerable.

Quantos explores a post-quantum-oriented design for new deployments. The current repository uses different PQC-compatible primitives by subsystem and does not yet define one uniform mainnet cryptographic profile. Hybrid migration and institutional key-management requirements remain deployment decisions.

1.3 Design Principles​

  • Post-quantum direction: Transaction signing, finality signing, P2P key establishment and selection proofs use distinct PQC-compatible code paths that must be audited and standardized before mainnet.
  • Honest Claims: Throughput, finality, and verification claims are qualified with their assumptions, directionality, and trust models.
  • Massive Parallelization: Horizontal scaling through dynamic sharding and DAG-based inclusion.
  • Zero-Gas Execution: STACC replaces per-transaction fees with stake-proportional bandwidth quotas, supplemented by state rent.
  • Cryptographic Interoperability: Native light client proofs where available; honest oracle attestation where light clients are infeasible.
  • Checkpoint finality: The node implements checkpoint-based finality; latency depends on configuration, validator participation and network conditions.
  • Cross-chain proof tooling: The L0 contains batch proof construction and chain-specific verifiers/relayers; trust and on-chain verification differ by target chain.