Interchain Abstract Accounts

Introduction

Abstract Accounts have the capability to control Accounts on any chain supporting Abstract over the Inter-Blockchain Communication (IBC) protocol through Interchain Abstract Accounts (ICAAs). ICAAs allow for any Abstract Account to control Accounts, contracts, and liquidity on any chain, offering a chain-abstracted experience users and developers in the Interchain ecosystem.

Designed with versatility in mind, ICAAs are able to execute messages locally and remotely, supporting both single- and multi-hop executions.

flowchart
    subgraph Account IBC
        direction LR
        subgraph Chain B
        A4[Account]
        end

        subgraph Chain A
        direction TB
        User2[fa:fa-user User] -- owns --> A3["Account"]
        A4[Account]
        end
        A3 -.IBC.-> A4
    end

Integrating with Interchain Abstract Accounts

Enabling IBC on the Account

Users must install the ibc-client contract on their account to enable IBC. To do so they can call the ExecuteMsg::InstallModules endpoint with the abstract:ibc-client module ID.

#![allow(unused)]
fn main() {
pub enum ExecuteMsg{
    InstallModules {
        // Module information (module_id and version)
        modules: Vec<ModuleInstallConfig>,
    },
    //...
}
}

(Optional) Create an account on the remote chain

After the initialization step, the account is ready to send messages across IBC. However, if you wish, you can customize the remote account metadata before sending any messages. The following message is executed on the account contract:

#![allow(unused)]
fn main() {
pub enum AccountExecuteMsg {
    ExecuteOnModule {
        module_id: "abstract:ibc-client",
        exec_msg: IbcClientExecuteMsg {
            Register {
                host_chain: "destination-chain",
                // Customizable parameters
                base_asset: None,
                namespace: None,
                install_modules: vec![],
            },
            ...,
        }
    }
    ...,
}
}

Account ID structure

The remote Interchain Abstract Account will have the same account sequence but will have a different trace. Let’s take an example. A account on Neutron with account sequence 42 wants to create accounts on Osmosis and Stargaze.

• Their account ID on Neutron is local-42.
• Their account ID on Osmosis is neutron-42.
• Their account ID on Stargaze is neutron-42 as well!

Remote accounts can create other remote accounts, and their traces will be chained. For instance, the neutron-42 account on Osmosis can create an account on Stargaze which will have the ID osmosis>neutron-42. This gives the ability to trace ICAAs back to their origin chain.

AccountTrace::Remote(vec!["neutron", "osmosis"])

Sending messages on remote accounts

With or without a pre-existing remote Account, Abstract Accounts are able to send messages on remote Accounts. The account_msgs will be executed in order on the remote account.

#![allow(unused)]
fn main() {
pub enum AccountExecuteMsg {
    ExecuteOnModule {
        module_id: "abstract:ibc-client",
        exec_msg: IbcClientExecuteMsg {
            RemoteAction{
                host_chain: "destination-chain",
                action: HostAction{
                    Dispatch{
                        account_msgs: Vec<AccountExecuteMsg { ... }>
                    },
                    ...,
                }
            },
            ...,
        }
    }
    ...,
}
}

Note that the two instances of the AccountExecuteMsg enum are the exact same type. This allows you to send multi-hop IBC messages. However, multi-hop transactions (of these kind) are not really something you would use often, unless you’re using another chain as a routing chain.

Specification of Interchain Abstract Accounts

The following specification specifies packet data structure, state machine handling logic, and encoding details for the transfer of messages and creation of Abstract accounts over an IBC channel between a client and a host on separate chains. The state machine logic presented allows for safe multi-chain account creation and execution.

Motivation

Users of a set of chains connected over the IBC protocol might wish to interact with smart-contracts and dapps present on another chain than their origin, while not having to onboard the remote chain, create a new wallet or transfer the necessary funds to this other chain. This application-layer standard describes a protocol for interacting with a remote chain and creating Abstract Account on chains connected with IBC which preserves asset ownership, limits the impact of Byzantine faults, and requires no additional permissioning.

Definitions

The Abstract IBC Account interface is described in the following guide and the specifications are roughly presented here

Desired Properties

• Preservation of account and funds ownership
• All interactions that can be done by a local account should be possible for a remote account as well.

Technical Specification

General mechanism

Abstract IBC capabilities are allowed by the ibc-client<->ibc-host pair. The ibc-client is responsible for authenticating the sender and sending packets across IBC to the ibc-host. The ibc-host is responsible for receiving packets and routing the packet to the corresponding contract on the remote chain. Under the hood,the client-host connection is handled by a Polytone channel. This allows Abstract to be interoperable with other protocols, more resilient to IBC constraints. However, Abstract is not bound to Polytone and any other IBC relaying protocol could be used for relaying packets. Here is a simple schematic that explains the different components of the Abstract IBC infrastructure.

flowchart LR

    subgraph Osmosis[Osmosis Chain]
        Osmosis-Abstract-Account -.-> Osmosis-Client
        Osmosis-Client --> Osmosis-Note
        subgraph Osmosis-Polytone[Polytone]
            Osmosis-Note
        end
    end


    subgraph Neutron[Neutron Chain]
        subgraph Neutron-Polytone[Polytone]
            Neutron-Voice -.-> Neutron-Proxy
        end
        Neutron-Proxy --> Neutron-Host
        Neutron-Host -.-> Neutron-Abstract-Account
    end

    Osmosis-Note ==IBC==> Neutron-Voice

You see that an Abstract Interchain connection is uni-directional. You need 2 connections to be able to interact bi-directionnally with Abstract. Up until today however, only a local account can act on a distant account and not the other way around. Here is an examples using AccountId between neutron and osmosis:

• local-42 on neutron CAN control neutron-42 on osmosis via IBC
• neutron-42 on osmosis CAN’T control local-42 on neutron

Account creation

Interchain Abstract Accounts are traditional Abstract Accounts controlled by the ibc-host. The ibc-host is the admin of the account and routes any packet sent by a remote account on the corresponding local account. When creating an abstract account, it is simply registered by the ibc-host using the account-factory just like any other account.

When an action is triggered by a remote account, the ibc-host does the following verifications:

• If an local account already exists on-chain for the remote account, it just dispatches the message to the account.
• If no account exists, it creates one with default metadata and THEN dispatches the messages to this new account.

The Account creation process is therefore not mandatory when interacting with Interchain Abstract Accounts. This is why when you create an Abstract Account, you automatically have an account on every connected chains!

Data Structures

Interchain Abstract Account communication is done via a single message structure:

#![allow(unused)]
fn main() {
pub enum IbcHostExecuteMsg{
    /// Allows for remote execution from the Polytone implementation
    #[cw_orch(fn_name("ibc_execute"))]
    Execute {
        account_id: AccountId,
        /// The address of the calling account id. This is used purely for the send-all-back method.
        /// We include it in all messages none-the-less to simplify the users life
        account_address: String,
        action: HostAction,
    },
    ...,
}
}

• account-id is the id of the local account calling the action.
• account_address is the address of the local account calling the action.
• action is the action that should be executed by the ibc-host on the remote account:

#![allow(unused)]
fn main() {
#[cosmwasm_schema::cw_serde]
#[non_exhaustive]
pub enum InternalAction {
    /// Registers a new account from a remote chain
    Register {
        name: Option<String>,
        description: Option<String>,
        link: Option<String>,
        namespace: Option<String>,
        install_modules: Vec<ModuleInstallConfig>,
    },
}

#[cosmwasm_schema::cw_serde]
#[non_exhaustive]
pub enum HelperAction {
    SendAllBack,
}

/// Callable actions on a remote host
#[cosmwasm_schema::cw_serde]
pub enum HostAction {
    /// Dispatch messages to a remote Account.
    /// Will create a new Account if required.
    Dispatch {
        account_msgs: Vec<account::ExecuteMsg>,
    },
    /// Can't be called by an account directly. These are permissioned messages that only the IBC Client is allowed to call by itself.
    Internal(InternalAction),
    /// Some helpers that allow calling dispatch messages faster (for actions that are called regularly)
    Helpers(HelperAction),
}
}

Acknowledgement and Callback

IBC works with 4 steps:

1. Sending a packet (Source chain)
2. Receiving a packet (Destination chain)
3. Sending an acknowledgement (Destination chain)
4. Receiving an acknowledgement (Source chain)

We have already covered the 2 first steps with the sections above. We cover the 2 lasts steps in this section.

Step 3 (sending an ack), is handled by Polytone. They catch any error that could happen during contract execution and send back an acknowledgement reflecting the state of the contract execution on the remote chain. This is handled through the Callback struct.

For Step 4, Polytone allows for sending a message to the initial sender of the IBC interaction after the packet was successfully received in the remote chain. Abstract DOESN’T use this feature for user actions, so callbacks are not possible when using Interchain Abstract Accounts. If you are a module developer, check out the Module Ibc section that allows for callbacks.

Abstract only uses Polytone Callbacks when:

• Registering a new Abstract IBC counterpart, to store the remote Polytone proxy caller.
• Creating remote accounts to be able to store the remote Abstract Account address locally.

Cross chain trace

Because accounts created across chains using the IAA protocol are controlled by an account located on a remote chain, the account that is calling the action needs to be related to the account on the remote chain. This is done through the AccountId struct. The IBC-host module leverages the AccountId::trace field of this struct. An account is wether AccountTrace::Local or AccountTrace::Remote. When a PacketMsg is sent across an IBC channel, the account id is transformed on the receiving chain in the following manner:

• If it was AccountTrace::Local before transfer, it turns into an AccountTrace::Remote account with one chain in the associated vector being the chain calling the PacketMsg (PacketMsg::client_chain)
• If it was AccountTrace::Remote before transfer, it stays remote and the client_chain field is pushed to the associated vector.

This allows full traceability of the account creations and calls.