# Overview Running on the PUT chain, Multi-sig contract deployment defines and realizes a common multi-sig service, which provides online multi-sig service for contracts. Contracts that need to access multi-sig can call the multi-sig program through CPI (Cross Program Invocation), while the private keys required for multi-sig are stored separately to avoid severe security problems caused by private key leakage. Multi-sig contracts mainly provide interfaces for creating multi-sig accounts, creating proposal accounts, as well as proposal voting and proposal verification. CPI calls the interface for multi-signature contracts, which we call the multi-signature interface. The normal flowchart for a multi-signature interface to access a multi-signature contract is roughly as follows.
1. Create a multi-signature account 2. Get the address for multi-signature accounts 3. Contract developers bind the multisig interface to a multisig account (decide which multisig account to use when developing the multisig interface) 4. Account Alice initiates the first multi-signature interface call 5. A transaction proposal is created on the first call and an account is created in the multi-signer by means of a Cross Program Invocation. The content of the transaction proposal is defined by the contract developer, and we recommend that the proposal outlines the user's actions (the proposal content for an A -> B transfer transaction can be written as "Alice (the proposal initiator) init a A transfer 1 PUT to B proposal.") 6. Alice gets the address of the proposal account and gets the successful response of execution 7. Alice, the initiator of the transaction, informs other signatories of the proposal address (proposal\_address) offline, and other signatories can vote after viewing the proposal 8. After the proposal is approved, Alice initiates a second multi-signature interface call 9. The multi-signature interface method verifies that the proposal has passed by calling the multi-signature contract through Cross Program Invocation 10. If the proposal is approved, the multi-signature interface starts executing the real contract logic 11. Return a successful response You can see that multi-signature contracts actually increase the complexity of the multi-signature interface, mainly because methods that were called once now need to be called twice by the initiator. However, multi-signature makes the contract interface more secure. From a security point of view, it is worth increasing code complexity.