Zycord Lab

Overture: a security upgrade, before the cEVM opens

Zycord v0.7.1, Overture: a mandatory network security upgrade

  • Testnet: block 69,120 (around October 29)
  • Mainnet: block 77,760 (around November 3)
  • Download: zycord.com/download, or zcd update

Overture is a security upgrade. We used the testing period to find and fix what had to be fixed before the cEVM opens on mainnet at block 80,640.

It is mandatory. Every node and every miner must run v0.7.1 before its network reaches the block above. An earlier release stops following the network there.

More than 40 security and stability fixes

  • Consensus: 4. Points an attacker could use to make nodes validate the cEVM differently. Every node now reaches the same result.
  • p2p: 7. Peers that tried to spend a node’s resources at no cost.
  • Sync: 7. A fake or cheap chain no longer captures a syncing node, and a new node syncs from genesis without stalling.
  • Mempool and sequencer: 6. Invalid requests are stopped before they take space or are relayed.
  • Stratum and storage: 5. Bans per host, and blocks found by a pool now reach the pool.
  • Wallet: 10. Files kept per network, key files protected on Windows, warnings shown before they can be accepted, and more.
  • Four more. The miner no longer pauses after a reorganization, mainnet pins checkpoints at blocks 2,880, 20,160 and 40,320, a rollback restores the spent-address registry correctly, and blocks in a format the network does not use are refused on arrival.

That is 43 in all.

The full write-up of each fix follows once most of the network has upgraded.

Highlight: safer upgrades from now on

From Overture on, network upgrades activate by version bits, the mechanism Bitcoin uses (BIP9). Each block signals whether its miner is ready, and a change activates only once 70% of blocks signal it.

No future upgrade has to bet on a fixed date: it waits until the network is ready. That greatly lowers the risk of a fork, and it is the main reason for this upgrade.

cEVM and smart contracts

Everything the testnet showed was applied before the opening.

Prices rebuilt. We measured the real cost of each cEVM operation and rebuilt the price table:

  • gas is priced in micro-drops, with lower and more accurate fees;
  • the skip fee falls from 1,000,000 to 1,000 drops;
  • ed25519_verify, blake3 and KECCAK256 are priced at their measured cost;
  • creating new state pays 1,000 drops per cell, and updates cost nothing extra.

Privacy. The cEVM gains the cryptographic operations that private contracts were missing:

  • Ristretto255, the basis for commitments and ring signatures;
  • bn254 and BLS12-381, to verify zero-knowledge proofs;
  • also p256verify (passkeys) and ecrecover, for compatibility.

Stability. The cEVM’s consensus rules are fixed so that every node validates the same way, and an intent can now be paid inside its own call (sponsored fills).

Tested

  • 174 black-box network tests, none skipped.
  • Each vulnerability test is shown to catch its bug in the previous release.

Check your version with zycordd --version. The full release notes are on GitLab.