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Multi-Signature Guide

There is a complete 2/3 multi-signature demo: https://github.com/MixinNetwork/trusted-group, the online test bot id: 7000101488.

A scenario where the multi-signature could be used: There is an asset that belongs to a team of three people, A, B, and C. Two of them need to agree to use this asset. In this case, a 2/3 multi-signature is appropriate.

A, B, C need to be three different bots or users of Mixin Network (private keys and PINs required).

1. Transfer an asset to the common account of A, B, and C. POST /transactions​

Transfer an asset to a multi-signature account, refer to the following document for more info. https://developers.mixin.one/document/wallet/api/transfer-to-multisigs

2. Get your own utxo /multisigs/outputs​

It should be noted that in a transaction, threshold and members must map to the same members, and the number of signatures (2 of 2/3) API document: https://developers.mixin.one/document/wallet/api/multisigs/outputs

We need to continuously request the api server, get the latest utxo and save it.

3. The withdrawal of assets, as mentioned above, requires at least two signatures to complete, but the process is the same​

There are 3 different operations related to multi-signature，which are signing, cancelling, and unlocking. A request needs to be constructed before every operation. API document: https://developers.mixin.one/document/wallet/api/multisigs/request

The Goal: A needs to withdraw 100 CNB from a common account.

  1. A sends a request (POST /multisigs/requests).
  2. A signs, POST /multisigs/requests/:id/sign，in which :id is request id.
  3. B, C need to do something similar. Take C as a example, in the outputs C receives，state is now signed, C takes the tx signed by A to repeat step 1 and 2, that is constructing the request and signing.
  4. Parse signed tx, and then check whether the number of signers is 2, if >= 2, send the transaction to mainnet.
  5. A now gets the 100 CNB, transaction complete.

Code for signing refund after a payment: https://github.com/MixinNetwork/trusted-group/blob/master/sample/models/payment.go#L164

During the process of contructing the transaction, A's GhostKeys will be used(one-time key), which can be retrieved at https://developers.mixin.one/document/wallet/api/network/keys .

4. Cancelling The Transaction​

  1. Construct the request, the process is the same as contructing a transaction.
  2. Send the cancel request, POST /multisigs/requests/:id/cancel，:id is request id. Note, only tx in the unspent state can be cancelled.

5. Unlocking The Transaction​

When the tx is signed but not sent, cacelling the tx means to unlock it, the process is a lot like cancelling.

  1. Construct the request, the process is the same as contructing a transaction.
  2. Send the request, POST /multisigs/requests/:id/unlock，:id is request id, Note that only signed tx can be cancelled.

Conclusion​

In most cases, only step 1, 2, and 3 are relavent. First deposit, then sign the related outputs and send the tx to mainnet to spend.