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Let's consider a situation where a bank wants to allow either 2 tellers or 1 manager to sign off on any transfer transaction over $500 and under $1000. In this case, the condition will be: Condition.asset("usd@nbc").qty(500).comparison(">").qty(1000).comparison("<") and the signatory_sets for the tellers and manager will be OR unioned, so that either the m-of-n signatues from the tellers or the single signature from the manager will be acceptable for transaction signing.
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Results
Second version of Iroha evolved the design of Iroha 1.x and can't use the same approach while it works to address requirements.
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The same way Multisignature transactions implementation can be done. Main questions should be answered before that.
Multisignature transaction identification
Given `M` as required amount of signatures to collect and `N` as a set of legal signatories Then if `M` is greater than 1 Transaction should be treated as Multisignature.
Signatories set
As mentioned in "Multisignature transaction identification" `N` is a set of legal signatories. What variants we can have in this set?
- One unique signatory of one account.
- Several unique signatories of one account.
- Several unique signatories of several accounts.
- Any signatories of one account.
- Any signatories of several accounts.
- ...
So how we can describe `N`?
| No Format |
|---|
enum N {
Quantity(usize),
Holders([AccountId]),
Set([Signatory]),
} |
In this case `Quantity` variant is less restrictive than goes `Holders` and `Set` as most restrictive.
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Configuration
Multisignature Transactions can be configured by a combination of `CheckSignatures` Iroha Special Instruction mandatory for every transaction with `N` Initial transaction's author Account's Asset.
If `CheckSignatures` passed successfully rest of instructions applied to the state. Otherwise transaction will be send to all peers.
Questions
- Should we guarantee persistence of Multisignature transactions waiting for required signatures on the ledger?
- Should we provide configuration of Multisignature without assets (client only)?
- How to merge Multisignature transactions signatures?