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Fonero updater

This document describes the mechanism to publish Fonero updates.

We use Codechain to secure our code against unwanted changes. The last signed source tree hash of the Codechain hashchain is published in the Fonero block headers.

Mechanism

  • Use two different Codechain hashchains, one for the Fonero mainnet and one for testnet (.codechain_mainnet and .codechain_testnet).
  • The mainnet and testnet Codechains have different sets of signers. The security requirements for testnet are less strict.
  • fnochain is a Codechain wrapper that calls codechain for mainnet and testnet. codechain publish -y is used internally to avoid reading the same patch twice.
  • Extend wire.BlockHeader with a CodechainHead [32]byte field to publish the current Codechain source tree hash used by the miner. Maybe ExtraData [32]byte could also be used for that.
  • Extend the wire format to distribute Codechain hashchain updates and patch files (details TBD):
    • Give me hashchain updates (between X and Y)
    • Give me entire hashchain
    • Give me patch
    • Similar methods for publishing (via fnoupdate)?
  • Miners manually update to a newly published version. As soon as a miner mines a block with the new header it activates on the network. Miners always write the version they are running on into the header.
  • Nodes either update automatically or manually. Automatic updates happen probabilistically (10% probability that a node updates in a given day, with manual override). This leads to a good code diversity in the network even in the case of automatic updates.
  • It is important that not every node updates to the newest version immediately, there should always be N versions of the code running on the network (with N between 3 and 5).
  • fnod has the corresponding Codechain hash compiled in and it verifies that it is a valid one and in the allowed window defined by N.
  • fnoupdate is used to publish an update to the network via the extended the wire protocol.

Wire protocol

  • MsgVersion & MsgVerAck
  • Encode current code version in MsgVersion.UserAgent or in separate field?