Suggestion for group currencies

Here is an implementation suggestion for group currencies.

Textual description:
A group currency would define a number of individual Circles tokens directly or transitively (all accounts trusted by account X) as members. All of those members Circles could be used to mint the group currency.

Because of the minting rule that always requires to use personal Circles all group currency will be “backed” (potentially transitively in layered groups) by personal Circles.

Optionally a group currency can offer to redeem group currency for underlying tokens. This can be restricted by additional rules or made available to anyone.
Optionally a fee can be charged for minting group currency and/or redeeming group currency.

is ERC20

owner // has admin rights - specifically adding and removing accounts to the group
redeemer // has the right to redeem group currency for underlying tokens (optional, can be public)

/* dictionary of (Circles) ERC20 addresses that are members - side note: we do not need to check that those tokens are personal Circles ERC20 - they could also be other group currencies to create layered groups*/
direct_members{} // address (ERC20 token) -> boolean

/* dictionary of Circles accounts (personal or shared accounts)
those act as trust delegates, if an account is trusted by an account in this dictionary it will be transitively a member*/
 delegated_trustees{} // address (account) -> boolean


   require(msg.sender = owner)
   direct_members[address] = true

   require(msg.sender = owner)
   direct_members[address] = false

/* potentially the same functions with batch functionality; equivalent for groups */

// Group currently is created from collateral tokens. Collateral is either directly part of the direct_members dictionary or trusted by someone in the delegated_trustees dictionary.
mint(trusted_by, collateral, amount):
   if trusted_by != 0:
      require(trusted_by in delegated_trustees)
   collateral.transer_from(from:msg.sender, to:this, amount=amount)
   mint amount * (1-mint-fee)
   // send minted amount to msg.sender

redeem(ERC20, amount)
   if redeemer != 0: require(msq.sender = redeemer)
   //burn group currency
   this.transfer_from(msg.sender, 0x0000, amount)
   //send ERC20 to redeemer
   account.transfer(msg.sender, amount)

Optional the group currency can register in the Circles WOT and trust all Circles that it would allow to use for minting (all members). This would allow others to make transitive transfers trough this account. The potential downside would be that the group currency would likely become only backed by the “weakest Circles” of the group instead of trough an average pool as anyone could extract more valuable Circles for the least valuable Circles that are part of the group.

P.S: One alternative way to add various redeem logic is to simply specify a contract (“treasury”) where Circles are sent to when used for minting. Any redeem logic in this case could be outsourced to the treasury contract. The simplest form would be to use a Safe (“Shared Wallet”) that would allow access to those Circles. More complex forms could be contracts that only allow access to those tokens by burning group tokens.


Nice! So in this scenario does it mean that the group currencies ‘hold’ personal currencies within them? In other words, minting would be based on the amount of personal currencies that are deposited to “back” it, which are in turn determined by the structure of trust right? How would this “enforced” deposit work in practice? Would it be a contract that defines that only the owner can mint/redeem? I think the underlying logic makes sense but would ask about the differences/benefits of group currencies being minted by “burning” personal currencies rather than having them stored somewhere. In that scenario, people can issue group currencies by putting together their personal currencies and then burn them to create a group currency. E.g. Ali, Bob and Carol all burn each 10 CRC and issue 30 ABC CRC group currency. In this scenario you cannot redeem back your personal currencies but it does allow for monetary destruction on an individual basis, which basically means that people can choose to add to a group currency and make one owned in common rather than individuals owning group currencies based on the trust network. Somewhat similar to Sarah Friend’s proposal. In general I think people should have both the power to issue and the power to redeem/destroy their CRC credits/tokens. This should give the system a lot more flexibility and resilience. Really cool and exciting suggestion!


This implementation suggestion leaves room for both (and even more) options.

  1. Group currency is minted by using the individual currency but it can never be redeemed again. (this is then basically the same as burning the individual currency)

  2. Anyone who holds a group can use it to claim one of the underlying individual Circles.

  3. (A compromise)
    One the group (e.g. a DAO or multi-sig) that represents the group can choose to redeem. E.g. maybe they want to merge with another group so they could decide to redeem all individual Circles and then put those into the other group.

I can see good reasons for all 3 options.

I created a prototype for this functionality here: circles-contracts/ at master · ice09/circles-contracts · GitHub

It implements the simple version without redeem but highly WIP, would love to get feedback on this.


There is a transitiveMint version of the GroupCurrencyToken now, however it would require a modified version of the Hub: OrgaHub. mint and mintDelegate also work with the existing Hub:

Added a centralized version which can work with the current version of the Hub contract, however this version is dependent on a centralized monitor service which triggers mintTransitive: see

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