Decommissioning of the 'transfer()' function on xDAI bridge

Background:

Currently, validators mint xDai on Gnosis whenever DAI tokens are transferred to the Gnosis xDAI bridge contract on Ethereum. This feature is in addition to the traditional method for bridging tokens (the relayTokens method). It was initially implemented to decrease gas costs on Ethereum to the absolute minimum. However, with the new Hashi implementation, adding support for validating a transfer will increase gas costs significantly, defeating its original purpose. Additionally, the transfer functionality is already sub-optimal as it does not properly adjust the bridge limits.

Solution:
The bridge will support ONLY relayTokens() function for minting xDAI. The bridge will NOT mint xDAI anymore if DAI is simply transferred to the bridge contract.

Potential Side Effects & Mitigation:

  1. Our Bridge UI uses currently transfer → We will change this to relayTokens asap.
  2. Gas for users will increase from 30k to 50k → The 50k gas is what users currently pay for using any 3rd party bridge (jumper, connext, hop) so nothing abnormally high.
  3. 3rd party Apps / Bridges using transfer → Highly unlikely as most use contracts to invoke the bridge (therefore relayTokens by default) but we will make sure that the changes are properly communicated.
  4. Some “whale”/ Market Maker or other actor that uses scripts to transact with the bridge → Communications as in 3. We will also implement a function to return funds in case they were transferred to the contract by mistake (to be called by the Governance Multisig 8-of-16)

Plan & Timeline:

  • The decommissioning will take place in September so we will have 3 months for communications and preparations
  • Communications campaign to inform the community on all channels (discord, twitter, telegram) on regular intervals till complete decommission.
  • We will monitor the activity of the bridge contract for “transfers” and we will make sure that the number tends to 0 as we are moving to the full bridge migration to Hashi.

Let me know if there are any questions and feedback on this.

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