Soundness Labs and Mysten Labs have developed PQ-Chain, a backward-compatible upgrade for EdDSA-based blockchains like Stellar, Solana, Sui, and Aptos that adds quantum resistance without hard forks or address changes. It leverages the existing quantum-secure seed in EdDSA keypairs, proven via PQ-NIZK proofs at the transaction and account levels. This opt-in approach provides immediate protection during the transition to native post-quantum signatures.
PQ-Chain offers a quantum-safe upgrade path for EdDSA chains including Stellar, Solana, Sui, and Aptos by activating a hidden quantum-resistant seed already present in every keypair, without requiring forks, address changes, or mass migrations. Users generate off-chain zkSNARK proofs demonstrating knowledge of their seed corresponding to the on-chain public key, which the chain verifies alongside traditional EdDSA signatures for dual protection. Transactions remain backward-compatible, allowing gradual opt-in adoption on a per-transaction basis. In the long term, it enables account-level migrations to post-quantum signatures like Falcon or Sphincs+ using the proven seed ownership, fostering cross-chain interoperable identity. This approach mitigates quantum threats—where adversaries could derive signing keys from public keys—while preserving existing infrastructure and user self-custody.
