Sign an Arbitrary Message

The signArbitrary and verifyArbitrary APIs enable off-chain proof of account ownership and message verification, adhering to the ADR-36 specification.

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signArbitrary

Function Signatures

This method allows you to request an ADR-36-compliant signature, primarily used for off-chain account ownership proofs. The signature is generated based on the provided data.

signArbitrary(
  chainId: string,
  signer: string,
  data: string | Uint8Array
): Promise<StdSignature>;

Parameters

Parameter	Type	Description
chainId	string	The chain ID of the chain for which the signature is being requested.
signer	string	The Bech32 address of the account that will sign the message.
data	string | Uint8Array	The arbitrary message to sign. If provided as a string, it will be displayed as plain text in the confirmation popup.

Return Value

It returns a Promise<StdSignature> that resolves to the signature object.

StdSignature Interface

interface StdSignature {
  readonly pub_key: PubKey;
  readonly signature: string;
}

Example Usage

const chainId = "cosmoshub-4";
const signer = "cosmos1...";
const data = "This is a test message";

const signature = await keplr.signArbitrary(chainId, signer, data);
console.log("Generated Signature:", signature);

It displays the popup as follows:

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ADR-36 Signing with signAmino

If you use the signAmino API with a sign doc formatted to meet ADR-36 requirements, it functions equivalently to signArbitrary. The required sign doc format is as follows:

1. Message Requirements:

   • The message should be a single message of type "sign/MsgSignData".
   • The message must include:
     • "signer": The account performing the signature.
     • "data": The message content, encoded in Base64.

2. Sign Doc Fields:

   • chain_id: Must be an empty string ("").
   • memo: Must be an empty string ("").
   • account_number: Must be "0".
   • sequence: Must be "0".
   • fee: Must be { gas: "0", amount: [] }.

Essential details about signAmino can be found in Amino Signing section in "Sign a Message" page.

Example Usage

const adr36SignData = async (chainId, signerAddress, message) => {
  // Base64 encode the message as required by ADR-36
  const base64Data = Buffer.from(message).toString("base64");

  // Create a sign doc compliant with ADR-36
  const signDoc = {
    chain_id: "",
    account_number: "0",
    sequence: "0",
    fee: { gas: "0", amount: [] },
    memo: "",
    msgs: [
    {
      type: "sign/MsgSignData",
      value: {
      signer: signerAddress,
      data: base64Data,
      },
    },
    ],
  };

  const signResponse = await keplr.signAmino(chainId, signerAddress, signDoc);

  console.log("Signed Document:", signResponse.signed);
  console.log("Signature:", signResponse.signature);

  return signResponse;
};

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verifyArbitrary

Function Signatures

This method verifies the result of an ADR-36 signature generated via the signArbitrary or signAmino API. verifyArbitrary is designed for simple usage and verifies the signature of the currently selected account only.

note

Recommendation: Use the verifyADR36Amino function from the @keplr-wallet/cosmos package or implement your own verification logic for more robust use cases.

verifyArbitrary(
  chainId: string,
  signer: string,
  data: string | Uint8Array,
  signature: StdSignature
): Promise<boolean>;

Parameters

Parameter	Type	Description
chainId	string	The chain ID of the chain for which the signature was created.
signer	string	The Bech32 address of the account used to create the signature.
data	string | Uint8Array	The original message that was signed.
signature	StdSignature	The signature object to verify.

Example Usage

const chainId = "cosmoshub-4";
const signer = "cosmos1...";
const data = "This is a test message";
const signature = {
  pub_key: { type: "tendermint/PubKeySecp256k1", value: "..." },
  signature: "...",
};

const isValid = await keplr.verifyArbitrary(chainId, signer, data, signature);

console.log("Is signature valid?", isValid);