Mobile Wallet Adapter specification

Mobile Wallet Adapter specification
Version
1. Changelog (oldest to newest)
  1. Pre-v1.0.0 changelog
Non-normative front matter
Specification
Support for other chains

Version

This specification uses semantic versioning

Version: 1.0.0

Changelog (oldest to newest)

Version	Description
1.0.0	Initial release version of the Mobile Wallet Adapter specification (identical to pre-release version 0.9.1)

Pre-v1.0.0 changelog

This is retained for historical reference only. None of these versions were official releases, and there are no guarantees of backward compatibility.

Version	Description
0.1.0	Initial draft
0.2.0	Updates based on wallet adapter feedback
0.2.1	Fix a few missed pluralizations
0.3.0	Sessions now track authorization statefully, rather than by providing `auth_token` to each privileged method
0.3.1	Enforce HTTPS for endpoint-specific URIs
0.3.2	Replace timeout placeholders with minimum timeouts
0.3.3	`sign_messages` should take multiple addresses for signing (for parity with `sign_transactions` behavior)
0.9.0	Advancing spec version to 0.9.0 (near-final version)
0.9.1	Integrate some review feedback

Non-normative front matter

The contents of this section attempt to explain this specification with context and goals, but do not form a formal part of the specification itself.

Summary

The goal of this specification is to define a protocol to expose Solana iOS and Android wallet app functionality (authorization and transaction signing) to dapps. It is optimized for use cases where the wallet app is running on a mobile device (Android or iOS), but does not preclude usage by wallets on a desktop OS (Linux, macOS, Windows, etc). This protocol is freely available to all Solana developers, and the intention is for this to become the standard for connecting all dapps to mobile wallet apps.

User stories

These user stories outline the goals and user experiences that this protocol aims to enable.

As a user, I want my phone to be a universal wallet for any transaction, regardless of where I am interacting with a dapp (i.e. on a single device, or on a different nearby device)
As a user, I want my dapp transactions to be private and secure
As a user, I want local dapp authorizations and transactions to be as simple as those I experience using the web-based wallet-adapter
As a user, I want my authorization of a dapp by my wallet to be a one-time operation
As a native dapp developer, I want my dapp to work with all native wallet apps
As a web dapp developer, I want my mobile browser friendly dapp to work with all native wallet apps
As a dapp or wallet app developer, I want permissively licensed open source reference implementations of the protocol to be available for my use

Requirements

These requirements are derived from the user stories, and exist to guide specification design decisions.

All communication between dapps and wallet apps should take place over a secure channel.

Rationale: this prevents transaction tampering and frontrunning.
At least one transport mechanism should be a standard web technology (for e.g. HTTP/S, WebSockets, etc).

Rationale: this supports using web-based dapps with native wallet apps.
The protocol must support one or more mechanisms to exchange a shared token (for e.g., URI links, QR codes, NFC, BT, etc), which shall be used to establish the secure channel.

Rationale: this protects against MITM attacks during secure channel establishment.
At least one shared token exchange mechanism must be available to remote browser-based dapps (e.g. displaying a QR code).

Rationale: this supports using remote dapps with native wallet apps.
The shared token must be able to establish a secure channel an indefinite number of times.

Rationale: this supports persistent dapp <-> wallet app connections after a one-time authorization.
For communication between a dapp and native wallet app running on a single device, the protocol must not require the use of a remote communication intermediary (though this does not preclude the optional use of one, at the discretion of the dapp and/or wallet app).

Rationale: a remote intermediate (such as a reflector server) increases both the communication latency and the attack surface (by intentionally introducing a 3rd party to communications).
The protocol must support a mechanism (such as a custom URI scheme) that allows launching a native app from a mobile web browser on both Android and iOS.

Rationale: the user should not be required to manually launch a wallet app for local wallet app interaction.
The dapp must identify itself to the wallet app during authorization.

Rationale: this allows the wallet app to give the user context about what they are authorizing.
The reference implementation(s) of the protocol should be Apache 2.0 licensed, and made available on a public repository.

Specification

Terminology

association token - a base64url encoding of an ECDSA public keypoint

dapp endpoint - an app implementing user-facing functionality (e.g. DeFi services, blockchain games, etc). This endpoint acts as both the initiator and the client in this protocol.

reflector - an intermediary which brokers connections between two endpoints, when they are unable to communicate directly themselves. It should be viewed as a potential adversary.

wallet endpoint - an app implementing wallet-like functionality (i.e. providing transaction signing services). This endpoint acts as the server in this protocol.

Transport

WebSockets

WebSockets is a mandatory transport protocol for mobile-wallet-adapter implementations. Dapp endpoints must be able to act as a WebSocket client, and wallet endpoints must be able to act as either a WebSocket server or client (depending on whether the connection is local, or if a reflector is used, respectively).

A WebSocket client API is available in all major browsers, enabling web-based dapps (both mobile and desktop) to use this transport.

When connecting to a Local URI, the dapp endpoint must request, and the wallet endpoint must respond with, the com.solana.mobilewalletadapter.v1 WebSocket subprotocol. When connecting to a Remote URI, the both the dapp and wallet endpoints must request, and the reflector server must respond with, both the com.solana.mobilewalletadapter.v1 and com.solana.mobilewalletadapter.v1.reflector WebSocket subprotocols.

When the wallet endpoint is acting as a WebSocket server, it must send periodic PING frames to the dapp endpoint.

Bluetooth LE

Bluetooth LE is an optional transport protocol for mobile-wallet-adapter implementations. It enforces a proximity requirement on the endpoints, which some users may find desirable from a security standpoint. It also eliminates the need for a reflector when connecting dapp and wallet endpoints running on different systems, removing an attack surface from the protocol.

A Web Bluetooth client API is available in many browsers, enabling web-based dapps (both mobile and desktop) to use this transport.

The details of this transport are not defined in this version of the mobile-wallet-adapter protocol. It is expected to be defined in a future protocol version.

Association

Association is the process of establishing a shared association identifier between a dapp endpoint and a wallet endpoint (with no requirement that these be running on the same system). An association is ephemeral - it persists only until the transport is disconnected. A new association is performed every time a dapp endpoint seeks to connect to a wallet endpoint.

Association keypair

The dapp endpoint should generate an ephemeral EC keypair on the P-256 curve, and encode the public keypoint Qa using the X9.62 public key format (0x04 || x || y). This public keypoint is then base64url-encoded, and the resulting string is called the association token. The private keypoint for this keypair will be used during session establishment.

Local URI

When running on Android or iOS, the dapp endpoint should first attempt to associate with a local wallet endpoint by opening a URI (either from within the browser for a web dapp, or directly from a native dapp) with the solana-wallet: scheme. The URI should be formatted as:

solana-wallet:/v1/associate/local?association=<association_token>&port=<port_number>

where:

association_token is as described above
port_number is a random number between 49152 and 65535

Once the URI is opened, the dapp endpoint should attempt to connect to the local WebSocket address, ws://localhost:<port_number>/solana-wallet, and proceed to Session establishment.

If the WebSocket transport is unavailable locally after no less than 30 seconds, the dapp endpoint should display user guidance (e.g. download a wallet) and optionally present the opportunity to connect to a remote wallet endpoint using one or more of the other association mechanisms.

Android

If a wallet endpoint is installed which has registered an Activity for this URI scheme and format, it will be launched. Upon launch via this URI, the wallet endpoint should start a WebSocket server on port port_number and begin listening for connections to /solana-wallet for no less than 10 seconds. This websocket server should only accept connections from the localhost.

Whether launched from a web browser or a native dapp endpoint, the Intent’s action will be android.intent.action.VIEW and the category will be android.intent.category.BROWSABLE. When launched by a web browser, no caller identity will be available, and as such, the referrer details available within the Intent cannot be used to verify the origin of the association. When launched by a native dapp endpoint, this Intent should be sent with startActivityForResult, allowing the wallet endpoint to query the caller identity. The result returned to the calling dapp endpoint is not specified.

iOS

iOS support is planned for a future version of this specification

Desktop

Since desktop OSes do not generally allow launching an app with a URI, a dapp endpoint should not attempt to use this association scheme. One or more of the other association mechanisms should be utilized instead.

Remote URI

When running on a desktop OS, or when connecting to a local wallet endpoint fails, the dapp endpoint may present a URI suitable for connection via a reflector WebSocket server, which will reflect traffic between two parties. The URI should be formatted as:

solana-wallet:/v1/associate/remote?association=<association_token>&reflector=<host_authority>&id=<reflector_unique_id>

where:

association_token is as described above
host_authority is the address of a publicly routable WebSocket server implementing the reflector protocol
reflector_unique_id is a number generated securely at random by the dapp endpoint, 0 ≤ n ≤ 2^53 - 1

This URI should be provided to the wallet endpoint through an out-of-band mechanism, detailed in the subsections below. Each of the dapp and wallet endpoints should attempt to connect to the WebSocket address wss://<host_authority>/reflect?id=<reflector_unique_id>. On connection, each endpoint should wait for the Reflector protocol to signal that the counterparty endpoint has connected.

The dapp endpoint must wait no less than 30 seconds for reflection to commence. The wallet endpoint must wait no less than 10 seconds for reflection to commence. If it does not commence, the endpoints will disconnect and present appropriate error messages to the user.

QR codes

Dapp endpoints must support displaying the remote URI to the user encoded as a QR code. After displaying a QR code, the dapp endpoint should connect to the specified reflector. Wallet endpoints on devices with a camera should support scanning QR codes within the app, receiving notifications from the system that a QR code encoding a remote URI has been received, or both. Upon receipt of a remote URI from a scanned QR code, the wallet endpoint should attempt to connect to the specified reflector.

Clipboard

Dapp endpoints may optionally also support copying the remote URI to the system clipboard. After copying the remote URI to the clipboard, the dapp endpoint should connect to the specified reflector. Wallet endpoints on desktop OSes should provide a method to accept a remote URI from the system clipboard. Upon receipt of a remote URI from the system clipboard, the wallet endpoint should attempt to connect to the specified reflector.

Endpoint-specific URIs

During Session Establishment, the wallet endpoint may return a URI prefix to use for future association attempts. This is expected to be used with App Links or Universal Links, to ensure that the desired wallet app is launched by the dapp. A dapp should reject URI prefixes with schemes other than https: for security reasons. If a dapp has been informed of a URI prefix for a wallet, it should use it with the same path elements and parameters provided as for the solana-wallet: URI scheme. For e.g., if an Android wallet endpoint handles App Links for solanaexamplewallet.io, it could provide a prefix of:

https://solanaexamplewallet.io/mobilewalletadapter

The dapp endpoint would then assemble the following URI to begin association with that wallet locally:

https://solanaexamplewallet.io/mobilewalletadapter/v1/associate/local?association=<association_token>&port=<port_number>

All other aspects of associating are identical to those specified in the relevant preceding section.

Bluetooth LE

Bluetooth LE session establishment is not defined in this version of the mobile-wallet-adapter protocol. It is expected to be defined in a future protocol version.

Session establishment

APP_PING

While the expectation is that the WebSocket server be responsible for periodically issuing PINGs to the client endpoint, the introduction of a reflector adds a requirement that the endpoints need to be notified when the counterparty is available.

An APP_PING is an empty message. It is sent by the reflector to each endpoint when both endpoints have connected to the reflector. On first connecting to a reflector, the endpoints should wait to receive this message before initiating any communications. After any other message has been received, the APP_PING message becomes a no-op, and should be ignored.

HELLO_REQ

Direction

Dapp endpoint to wallet endpoint

Specification

<Qd><Sa>

where:

Qd: the X9.62-encoded dapp endpoint ephemeral ECDH public keypoint
Sa: a P1363-encoded ECDSA-SHA256 signature of Qd using the association keypair

Description

The HELLO_REQ message is the first message sent after a connection is established between the endpoints, and begins a Diffie-Hellman-Merkle key exchange. The dapp endpoint generates an ephemeral P-256 EC keypair and X9.62-encodes the public keypoint Qd. This encoded public keypoint is then ECDSA-SHA256-signed with the private keypoint of the association keypair, and the P1363-encoded signature appended to the encoded Qd public keypoint to form the HELLO_REQ message. The private keypoint of the P-256 EC keypair is retained for use on receipt of the HELLO_RSP message.

On receipt, the wallet endpoint should verify the signature of Qd using the association token. If signature verification is successful, the wallet endpoint should prepare and send a HELLO_RSP message to the dapp endpoint.

If qd signature verification fails, if no HELLO_REQ message is received by the wallet endpoint within no less than 10 seconds, or if a second HELLO_REQ message is received by the wallet endpoint at any time during the connection, all ephemeral key materials should be discarded, and the connection should be closed.

HELLO_RSP

Direction

Wallet endpoint to dapp endpoint

Specification

<Qw>

where:

Qw: the X9.62-encoded wallet endpoint ephemeral ECDH public keypoint

Description

In response to a valid HELLO_REQ message to the wallet endpoint (which should be the first message received after a connection is established between the endpoints), it should generate a P-256 EC keypair and X9.62-encode the public keypoint Qw. This encoded public keypoint Qw forms the HELLO_RSP message.

Upon sending of the HELLO_RSP message by the wallet endpoint, and receipt of the HELLO_RSP message by the dapp endpoint, each endpoint is now in possession of all necessary key materials to generate a shared secret for the chosen encryption algorithm, using the ECDH (as specified by NIST SP 800-56A) and HKDF (as specified by RFC5869) algorithms with the following KDF parameters:

ikm: the 32-byte ECDH-derived secret
salt: the 65 byte X9.62-encoded public keypoint Qa of the association keypair
L: 16 bytes (such that the output of the HKDF may be used directly as an AES-128 key)

Once each endpoint has calculated the ephemeral shared secret, they should proceed to providing or consuming the Wallet RPC interface.

If either public keypoint Qd or Qw is not valid, if no HELLO_RSP message is received by the dapp endpoint within no less than 10 seconds, or if a second HELLO_RSP message is received by the dapp endpoint at any time during the connection, all ephemeral key materials should be discarded, and the connection should be closed.

Wallet RPC interface

Operation

After session establishment completes, the wallet endpoint is ready to accept JSON-RPC 2.0 non-privileged method calls from the dapp endpoint. To invoke privileged methods, a dapp endpoint must first put the session into an authorized state via either an authorize or a reauthorize method call. For details on how a session enters and exits an authorized state, see the non-privileged methods.

Encrypted message wrapping

After the session establishment process completes, every message received by an endpoint is expected to be encrypted with AES-128-GCM (as specified by NIST SP 800-38D). The sending endpoint should prepare the encrypted message by concatenating:

the message sequence number, a 4-byte big-endian unsigned integer
a random 12-byte IV (which should be newly generated for each encrypted message)
the AES-128-GCM message ciphertext, encrypted using the private key created during session establishment and the random IV, and including the 4-byte message sequence number as additional authorized data (AAD)
the 16-byte authentication tag generated during AES-128-GCM encryption

After decrypting the ciphertext with the shared secret generated during session establishment and verifying the authentication tag, the receiving endpoint should further interpret it as a JSON-RPC 2.0 message.

The message sequence number is monotonically increasing, and starts at 1 when session establishment completes. Each endpoint maintains its own independent sequence number, and increments it by 1 each time an encrypted message is created and sent. On receipt of an encrypted message, each endpoint should verify that the sequence number is 1 greater than that of the previous message received (other than for the first message received). On receipt of a message with a sequence number set to anything other than the expected next value, the encrypted message should be discarded and the connection closed.

Non-normative commentary

Why does the protocol specify this, rather than rely on, e.g., TLS?

In remote usage, a reflector server is used to mediate a connection between a dapp and wallet endpoint. This reflector is viewed as an adversary, and so should not have access to the plaintext of endpoint communications.
This protocol supports multiple transports (i.e. ws: for local connections, wss: for reflector connections, Bluetooth LE for wireless connections). Each of these has different confidentiality and authenticity guarantees. By encrypting messages at the application layer, the protocol can provide a uniform minimum security guarantee for a heterogeneous set of transports.

Non-privileged methods

Non-privileged methods do not require the current session to be in an authorized state to invoke them (though they may still accept an auth_token to provide their functionality).

authorize

JSON-RPC method specification

Method

authorize

Params

{
    “identity”: {
        “uri”: “<dapp_uri>”,
        “icon”: “<dapp_icon_relative_path>”,
        “name”: “<dapp_name>”,
    },
    "cluster": "<cluster>",
}

where:

identity: a JSON object, containing:
- uri: (optional) a URI representing the web address associated with the dapp endpoint making this authorization request. If present, it must be an absolute, hierarchical URI.
- icon: (optional) a relative path (from uri) to an image asset file of an icon identifying the dapp endpoint making this authorization request
- name: (optional) the display name for this dapp endpoint
cluster: (optional) if set, the Solana network cluster with which the dapp endpoint intends to interact; supported values include mainnet-beta, testnet, devnet. If not set, defaults to mainnet-beta.

Result

{
    “auth_token”: “<auth_token>”,
    “accounts”: [
        {“address”: “<address>", “label”: “<label>”},
        ...
    ],
    “wallet_uri_base”: “<wallet_uri_base>”,
}

where:

auth_token: an opaque string representing a unique identifying token issued by the wallet endpoint to the dapp endpoint. The format and contents are an implementation detail of the wallet endpoint. The dapp endpoint can use this on future connections to reauthorize access to privileged methods.
accounts: one or more value objects that represent the accounts to which this auth token corresponds. These objects hold the following properties:
- address: a base64-encoded address for this account
- label: (optional) a human-readable string that describes the account. Wallet endpoints that allow their users to label their accounts may choose to return those labels here to enhance the user experience at the dapp endpoint.
wallet_uri_base: (optional) if this wallet endpoint has an endpoint-specific URI that the dapp endpoint should use for subsequent connections, this member will be included in the result object. The dapp endpoint should use this URI for all subsequent connections where it expects to use this auth_token.

Errors

-32602 (Invalid params) if the params object does not match the format defined above
ERROR_AUTHORIZATION_FAILED if the wallet endpoint did not authorize access to the requested privileged methods
ERROR_CLUSTER_NOT_SUPPORTED if the wallet endpoint does not support the requested Solana cluster

Description

This method allows the dapp endpoint to request authorization from the wallet endpoint for access to privileged methods. On success, it returns an auth_token providing access to privileged methods, along with addresses and optional labels for all authorized accounts. It may also return a URI suitable for future use as an endpoint-specific URI. After a successful call to authorize, the current session will be placed into an authorized state, with privileges associated with the returned auth_token. On failure, the current session with be placed into the unauthorized state.

The returned auth_token is an opaque string with meaning only to the wallet endpoint which created it. It is recommended that the wallet endpoint include a mechanism to authenticate the contents of auth tokens it issues (for e.g., with an HMAC, or by encryption with a secret symmetric key). This auth_token may be used to reauthorize future sessions between these dapp and wallet endpoints.

Dapp endpoints should make every effort possible to verify the authenticity of the presented identity. While the uri parameter is optional, it is strongly recommended - without it, the wallet endpoint may not be able to verify the authenticity of the dapp.

The cluster parameter allows the dapp endpoint to select a specific Solana cluster with which to interact. This is relevant for both sign_transactions, where a wallet may refuse to sign transactions without a currently valid blockhash, and for sign_and_send_transactions, where the wallet endpoint must know which cluster to submit the transactions to. This parameter would normally be used to select a cluster other than mainnet-beta for dapp development and testing purposes. Under normal circumstances, this field should be omitted, in which case the wallet endpoint will interact with the mainnet-beta cluster.

deauthorize

JSON-RPC method specification

Method

deauthorize

Params

{
    “auth_token”: “<auth_token>”,
}

where:

auth_token: an opaque string previously returned by a call to authorize, reauthorize, or clone_authorization

Result

{}

Errors

-32602 (Invalid params) if the params object does not match the format defined above

Description

This method will make the provided auth_token invalid for use (if it ever was valid). To avoid disclosure, this method will not indicate whether the auth_token was previously valid to the caller.

If, during the current session, the specified auth token was returned by the most recent call to authorize or reauthorize, the session with be placed into the unauthorized state.

reauthorize

JSON-RPC method specification

Method

reauthorize

Params

{
    “identity”: {
        “uri”: “<dapp_uri>”,
        “icon”: “<dapp_icon_relative_path>”,
        “name”: “<dapp_name>”,
    },
    “auth_token”: “<auth_token>”,
}

where:

identity: as defined for authorize
auth_token: an opaque string previously returned by a call to authorize, reauthorize, or clone_authorization

Result

{
    “auth_token”: “<auth_token>”,
    “accounts”: [
        {“address”: “<address>", “label”: “<label>”},
        ...
    ],
    “wallet_uri_base”: “<wallet_uri_base>”,
}

where:

auth_token: as defined for authorize
accounts: as defined for authorize
wallet_uri_base: as defined for authorize

Errors

-32602 (Invalid params) if the params object does not match the format defined above
ERROR_AUTHORIZATION_FAILED if the wallet endpoint declined to authorize the current session with auth_token for any reason

Description

This method attempts to put the current session in an authorized state, with privileges associated with the specified auth_token.

On success, the current session will be placed into an authorized state. Additionally, updated values for auth_token, accounts, and/or wallet_uri_base will be returned. These may differ from those originally provided in the authorize response for this auth token; if so, they override any previous values for these parameters. The prior values should be discarded and not reused. This allows a wallet endpoint to update the auth token used by the dapp endpoint, or to modify the set of authorized account addresses or their labels without requiring the dapp endpoint to restart the authorization process.

If the result is ERROR_AUTHORIZATION_FAILED, this auth token cannot be reused, and should be discarded. The dapp endpoint should request a new token with the authorize method. The session with be placed into the unauthorized state.

Non-normative commentary

reauthorize is intended to be a lightweight operation, as compared to authorize. It normally should not present any UI to the user, but instead perform only the subset of dapp endpoint identity checks that can be performed quickly and without user intervention. The intent is to quickly verify that an auth token remains valid for use by this dapp endpoint. If verification fails for any reason, the wallet endpoint should report ERROR_AUTHORIZATION_FAILED to the dapp endpoint, which would then discard the stored auth token and begin authorization from scratch with a new call to authorize.

Wallet endpoints should balance the responsibility for performing these identity checks against their latency impact. For example, a wallet endpoint may choose to accept an auth token issued in the last several minutes without performing any additional checks, but require dapp endpoint identity checks to be performed for an auth token that was issued before then. This facilitates multiple sessions to be established in a short timespan, related to the same user interaction with a dapp endpoint. The auth token validity policy is a competency of the wallet endpoint, and dictating any specific auth token lifespan or timeout is outside the scope of this protocol specification. However, it is strongly recommended that wallet endpoints do not issue auth tokens with unlimited lifespans or for which dapp endpoint identity checks are never performed on reauthorize.

get_capabilities

JSON-RPC method specification

Method

get_capabilities

Params

{}

Result

{
    "supports_clone_authorization": <supports_clone_authorization>,
    "supports_sign_and_send_transactions": <supports_sign_and_send_transactions>,
    "max_transactions_per_request": <max_transactions_per_request>,
    "max_messages_per_request": <max_messages_per_request>,
    "supported_transaction_versions": [<supported_transaction_versions>, ...]
}

where:

supports_clone_authorization: true if the clone_authorization method is supported, otherwise false
supports_sign_and_send_transactions: true if the sign_and_send_transactions method is supported, otherwise false
max_transactions_per_request: (optional) if present, the max number of transaction payloads which can be signed by a single sign_transactions or sign_and_send_transactions request. If absent, the implementation doesn’t publish a specific limit for this parameter.
max_messages_per_request: (optional) if present, the max number of transaction payloads which can be signed by a single sign_messages request. If absent, the implementation doesn’t publish a specific limit for this parameter.
supported_transaction_versions: the Solana network transaction formats supported by this wallet endpoint. Allowed values are those defined for TransactionVersion (for e.g., "legacy", 0, etc).

Errors

-32602 (Invalid params) if the params object does not match the format defined above

Description

This method can be used to enumerate the capabilities and limits of a wallet endpoint’s implementation of this specification. It returns whether optional specification features are supported, as well as any implementation-specific limits.

Privileged methods

Privileged methods require the current session to be in an authorized state to invoke them. For details on how a session enters and exits an authorized state, see the non-privileged methods.

sign_transactions

JSON-RPC method specification

Method

sign_transactions

Params

{
    “payloads”: [“<transaction>”, ...],
}

where:

payloads: one or more base64-encoded transaction payloads to sign

Result

{
    “signed_payloads”: [“<signed_transaction>”, ...],
}

where:

signed_payloads: the corresponding base64-encoded signed transaction payloads

Errors

-32602 (Invalid params) if the params object does not match the format defined above
ERROR_AUTHORIZATION_FAILED if the current session is in the unauthorized state, either because authorize or reauthorize has not been invoked for the current session, or because the current session’s authorization has been revoked by the wallet endpoint
ERROR_INVALID_PAYLOADS
```
“data”: {
    “valid”: [<transaction_valid>, ...],
}
```
if any transaction does not represent a valid transaction for signing, where:
- valid: an array of booleans with the same length as payloads indicating which are valid
ERROR_NOT_SIGNED if the wallet endpoint declined to sign these transactions for any reason
ERROR_TOO_MANY_PAYLOADS if the wallet endpoint is unable to sign all transactions due to exceeding implementation limits. These limits may be available via get_capabilities.

Description

The wallet endpoint should attempt to simulate the transactions provided by data and present them to the user for approval (if applicable). If approved (or if it does not require approval), the wallet endpoint should sign the transactions with the private keys for the requested authorized account addresses, and return the signed transactions to the dapp endpoint.

sign_and_send_transactions

JSON-RPC method specification

Method

sign_and_send_transactions

Params

{
    “payloads”: [“<transaction>”, ...],
    "options": {
        “min_context_slot”: <min_context_slot>,
    }
}

where:

payloads: one or more base64-encoded transaction payload to sign
options: (optional) a JSON object, containing:
- min_context_slot: (optional) if set, the minimum slot number at which to perform preflight transaction checks

Result

{
    “signatures”: [“<transaction_signature>”, ...],
}

where:

signatures: the corresponding base64-encoded transaction signatures

Errors

-32602 (Invalid params) if the params object does not match the format defined above
-32601 (Method not found) if sign_and_send_transactions is not supported by this wallet endpoint
ERROR_AUTHORIZATION_FAILED if the current session is in the unauthorized state, either because authorize or reauthorize has not been invoked for the current session, or because the current session’s authorization has been revoked by the wallet endpoint
ERROR_INVALID_PAYLOADS
```
“data”: {
    “valid”: [<transaction_valid>, ...]
}
```
if any transaction does not represent a valid transaction for signing, where:
- transaction_valid: an array of booleans with the same length as payloads indicating which are valid
ERROR_NOT_SIGNED if the wallet endpoint declined to sign this transaction for any reason
ERROR_NOT_SUBMITTED
```
“data”: {
    “signatures”: [“<transaction_signature>”, ...],
}
```
if the wallet endpoint was unable to submit one or more of the signed transactions to the network, where:
- signatures: the corresponding base64-encoded transaction signatures for transactions which were successfully sent to the network, or null for transactions which were unable to be submitted to the network for any reason
ERROR_TOO_MANY_PAYLOADS if the wallet endpoint is unable to sign all transactions due to exceeding implementation limits. These limits may be available via get_capabilities.

Description

Implementation of this method by a wallet endpoint is optional.

The wallet endpoint should attempt to simulate the transactions provided by payloads and present them to the user for approval (if applicable). If approved (or if it does not require approval), the wallet endpoint should verify the transactions, sign them with the private keys for the authorized addresses, submit them to the network, and return the transaction signatures to the dapp endpoint.

options allows customization of how the wallet endpoint processes the transactions it sends to the Solana network. If specified, min_context_slot specifies the minimum slot number that the transactions should be evaluated at. This allows the wallet endpoint to wait for its network RPC node to reach the same point in time as the node used by the dapp endpoint, ensuring that, e.g., the recent blockhash encoded in the transactions will be available.

Non-normative commentary

This method is optional, to support signing-only wallet endpoints which do not have any form of network connectivity.

it does not allow the dapp endpoint to specify the network RPC server to submit the transaction to; that is at the discretion of the wallet endpoint. If this is a detail that matters to the dapp endpoint, it should instead use the sign_transactions method and submit the transaction to a network RPC server of its choosing.

It is recommended that dapp endpoints verify that each transaction reached an appropriate level of commitment (typically either confirmed or finalized).

sign_messages

JSON-RPC method specification

Method

sign_messages

Params

{
    "addresses": ["<address>", ...],
    “payloads”: [“<message>”, ...],
}

where:

addresses: one or more base64-encoded addresses of the accounts which should be used to sign message. These should be a subset of the addresses returned by authorize or reauthorize for the current session’s authorization.
payloads: one or more base64url-encoded message payloads to sign

Result

{
    “signed_payloads”: [“<signed_message>”, ...],
}

where:

signed_payloads: the corresponding base64-encoded signed message payloads

Errors

-32602 (Invalid params) if the params object does not match the format defined above
ERROR_AUTHORIZATION_FAILED if the current session is in the unauthorized state, either because authorize or reauthorize has not been invoked for the current session, or because the current session’s authorization has been revoked by the wallet endpoint
ERROR_INVALID_PAYLOADS
```
“data”: {
    “valid”: [<message_valid>, ...],
}
```
if any message does not represent a valid message for signing, where:
- message_valid: an array of booleans with the same length as payloads indicating which are valid
ERROR_NOT_SIGNED if the wallet endpoint declined to sign these messages for any reason
ERROR_TOO_MANY_PAYLOADS if the wallet endpoint is unable to sign all messages due to exceeding implementation limits. These limits may be available via get_capabilities.

Description

The wallet endpoint should present the provided messages for approval. If approved, the wallet endpoint should sign the messages with the private key for the authorized account address, and return the signed messages to the dapp endpoint. The signatures should be appended to the message, in the same order as addresses.

clone_authorization

JSON-RPC method specification

Method

clone_authorization

Params

{}

Result

{
    “auth_token”: “<auth_token>”,
}

where:

auth_token: as defined for authorize

Errors

-32602 (Invalid params) if the params object does not match the format defined above
-32601 (Method not found) if clone_authorization is not supported by this wallet endpoint
ERROR_AUTHORIZATION_FAILED if the current session is in the unauthorized state, either because authorize or reauthorize has not been invoked for the current session, or because the current session’s authorization has been revoked by the wallet endpoint
ERROR_NOT_CLONED if the wallet endpoint declined to clone the current authorization for any reason

Description

Implementation of this method by a wallet endpoint is optional.

This method attempts to clone the session’s currently active authorization in a form suitable for sharing with another instance of the dapp endpoint, possibly running on a different system. Whether or not the wallet endpoint supports cloning an auth_token is an implementation detail. If this method succeeds, it will return an auth_token appropriate for sharing with another instance of the same dapp endpoint.

Non-normative commentary

The clone_authorization method enables sharing of an authorization between related instances of a dapp endpoint (for example, running on a mobile device and a desktop OS). This is a sensitive operation; dapp endpoints must endeavor to transfer the token securely between dapp endpoint instances. The ability of wallet endpoints to validate the identity of the holder of the cloned token is an implementation detail, and may be weaker than that of the original token. As such, not all wallet endpoints are expected to support this feature.

Constants

The protocol defines the following constants:

const ERROR_AUTHORIZATION_FAILED = -1
const ERROR_INVALID_PAYLOADS = -2
const ERROR_NOT_SIGNED = -3
const ERROR_NOT_SUBMITTED = -4
const ERROR_NOT_CLONED = -5
const ERROR_TOO_MANY_PAYLOADS = -6
const ERROR_CLUSTER_NOT_SUPPORTED = -7

const ERROR_ATTEST_ORIGIN_ANDROID = -100

Illustrative diagrams

Session establishment

Encrypted message wrapping

Authorize and sign transaction

Reauthorize and sign transaction

Dapp identity verification

Dapp endpoint identity verification is domain-based - through various platform-specific mechanisms, a dapp endpoint attests to the wallet that it is associated with a specific web domain. Wallet endpoints are responsible for deciding whether to extend trust to each dapp based on the attested web domain.

Android

Native dapp

Identity verification on Android relies on Digital Asset Links to associate apps with a web domain. Both native wallet apps and native dapps on Android should:

Be identified by package name and signing key fingerprint in a /.well-known/assetlinks.json file hosted on the web domain of the app developer
Use App Links for all Activity <intent-filter> elements in the app manifest that accept the web domain, (or any subdomain)

Failure to establish these Digital Asset Links will result in the inability of wallet endpoints to verify the identity of dapp endpoints, and puts the users’ funds at risk from malicious dapps.

Native dapp endpoints are required to associate with the wallet endpoint using either a Local URI or an Endpoint-specific URI, started via an Intent with startActivityForResult. This allows the wallet endpoint to retrieve the calling package identity, with getCallingPackage.

To verify the authenticity of the identity provided to authorize, the wallet endpoint should check the Digital Asset Link for the identity element URI and ensure that the calling package is signed with a certificate listed in an android_app statement within the Digital Asset Link file.

If the identity element does not contain a URI, or if the dapp endpoint’s calling package cannot be verified against an android_app target in the Digital Asset Link file, it is recommended that wallet endpoints decline to issue an authorization token to the dapp endpoint and return ERROR_AUTHORIZATION_FAILED.

Web dapp

Chromium (and related browsers, such as Chrome) associate with the wallet endpoint using either a Local URI or an Endpoint-specific URI, started via an Intent with startActivity, which does not provide the calling identity. In addition, EXTRA_REFERRER may not always be provided in the Intent, and even if it is, it is not a secure source of identity on Android. To provide dapp endpoint identity verification, a different method is required.

The browser security sandbox can attest to the origin of a web dapp endpoint, but only within the confines of the sandbox. To extend trust from the browser to the wallet endpoint, it must be brought into the browser security model. Trusted Web Activities enable this by allowing a verifiable postMessage channel to be established between the native wallet app and the web browser (once again, using Digital Asset Links). Once a channel is established, the wallet app can request that a trusted script running within the browser attest to the identity of the dapp.

The wallet endpoint’s software developer must host an HTML document containing an attestation script on a web domain whose Digital Asset Link file contains an android_app target verifying the wallet endpoint app. This attestation script is responsible for:

Generating an attestation keypair for the wallet endpoint, and issuing the public key to it
Attesting to the origin of dapp endpoints, by signing an attestation payload with the requested private key

The contents of this script are an implementation detail of wallet endpoints.

On an authorize, reauthorize, or clone_authorization attempt from a local web dapp endpoint, the wallet endpoint should check if the provided identity has been authorized during this session. If not, it should return ERROR_ATTEST_ORIGIN_ANDROID with an identity challenge. The dapp endpoint should load the identity attestation script and use postMessage to convey the dapp endpoint’s origin and the wallet endpoint challenge. The attestation script should construct a response to the challenge containing the origin, sign it with the corresponding wallet attestation private key, and return it to the dapp endpoint. The dapp endpoint should reattempt the failed authorization request, including the attestation response.

authorize, reauthorize, and clone_authorization modifications

Method

authorize, reauthorize, clone_authorization

Params

{
    ...,
    “attest_origin”: “<attest_origin_token>”,
}

where:

attest_origin_token: a token, generated by attest_origin_uri, from which the wallet endpoint can verify the authenticity of the identity parameter to this method

Result

No changes

Errors

...
ERROR_ATTEST_ORIGIN_ANDROID
“data”: {
    “context”: “<context>”,
    “challenge”: “<challenge>”,
    “attest_origin_uri”: “<uri>”,
}

if the identity provided in params requires verification, where:

context: the attestation context (for e.g., a key ID)
challenge: a base64-encoded challenge nonce uniquely identifying this attestation request
uri: the URI of the wallet endpoint HTML document containing the attestation script

On receipt of an ERROR_ATTEST_ORIGIN_ANDROID response, the dapp endpoint should decode the challenge nonce, construct the string “attest-origin” || decoded_challenge || session_secret, calculate the SHA256 hash of this string, and base64-encode the result. This value, h, binds challenge to this dapp endpoint (by including the session secret). It should then construct the JSON message:

{
    “m: “origin-attest”,
    “h”: <h>,
    “context”: <context>,
}

The dapp endpoint should load origin_attest_uri into an invisible iframe, and postMessage(origin_attest_msg) to it. The dapp endpoint should then await a response message from the iframe (via a message event listener). On receipt, the dapp endpoint should destroy the iframe, and reattempt the authorization request to the wallet endpoint, including the returned message contents as the attest_origin parameter.

Non-normative commentary

Many of the details of this identity verification process are left as an implementation detail of the wallet endpoint. However, as an illustrative example, here is one scheme which could be used to implement identity verification.

This approach uses a Custom Tab (possibly in Trusted Web Activity mode) with the same browser backend as the association request to securely create the attestation keypair, which is stored in local storage of the wallet endpoints web domain (from which the origin attestation script is fetched). The public keypoint is returned and stored by the wallet.

When the wallet determines that an origin attestation is necessary, it returns this same origin attestation script URI to the dapp endpoint, along with the challenge parameters. The dapp endpoint constructs the appropriate origin attestation message, opens the attestation script in an iframe, and sends it the message using postMessage. This provides the dapp endpoint origin to the attestation script, signed with the private keypoint. This message is returned to the dapp endpoint, which then reattempts the authorization request with the message as the attest_origin parameter. The wallet endpoint is able to use the corresponding public keypoint to validate the authenticity of this message, and then subsequently validate the dapp endpoint identity using the token payload.

iOS

iOS support is planned for a future version of this specification

Remote

No dapp endpoint verification method is defined by this version of the mobile-wallet-adapter protocol. Wallet endpoints are free to perform whatever implementation-specific verification techniques they desire (including rejecting all remote dapp endpoint authorization requests as unverified).

If a wallet endpoint supports the clone_authorization method, at a minimum it should also support reauthorize on the resulting auth token from a remote dapp endpoint.

Reflector protocol

Reflection is an extremely simple protocol; it will reflect all communications received from each endpoint to the other endpoint, up to a maximum size of 4KB per frame.

The reflector should listen for WebSocket secure connections to:

wss://<host_authority>/reflect?id=<reflector_unique_id>

The reflector will maintain two data sets:

Half open reflections - this set contains endpoint connections which are waiting for their corresponding counterparty to connect, along with the connection established time
Fully open reflections - this set contains endpoint connections for which the corresponding counterparty has connected, along with the reflection established time

On a new connection, the reflector will take the following action:

If there is an entry in the fully open reflections data set for the specified reflector_unique_id, the connection will be closed immediately
If there is an entry in the half open reflections data set for the specified reflector_unique_id, that entry will be removed and a new entry added to the fully open reflections data set for the connection pair. Reflection will be started for this connection pair.
Otherwise, an entry will be added to the half open reflections data set for this connection. All incoming data on this connection will be silently discarded.

When reflection begins, the reflector will send an APP_PING message to each connection, and then begin transmitting all messages received from each connection to the other connection in the pair.

On a disconnection:

If the connection is part of the fully open reflections data set, the entry will be removed and the other connection closed as well
Otherwise, the entry for the connection will be removed from the half-open reflections data set

Entries in the half open data set should be removed, and the connection closed, if still present in this set no less than 30 seconds after being added. Entries in the fully open data set should be removed, and both connections closed, if still present in this set no less than 90 seconds after being added. Entries in either data set may also be removed, and the connection(s) closed, before these time periods have elapsed at the discretion of the reflector (for e.g., during periods of limited resource availability).

To ensure that all active connections are maintained, the reflector shall ensure that periodic PING frames are sent to each connection.

Support for other chains

While the initial version of this specification is designed to support the Solana network, future support for other chain types is envisioned. This could be accomplished with:

modified association URIs (using schemes of the form newchain-wallet:// instead of solana-wallet://)
modified parameters to the RPC methods
- authorize would have a different set of chain identifiers
- get_capabilities would be used to express domain-specific capabilities relevant to the chain
- sign_and_send_transactions would use chain-specific shapes for the options object

The specifics of the application of Mobile Wallet Adapter to each additional chain would be captured either with an update to this specification, or an extension accompanying this specification, as appropriate.