> For the complete documentation index, see [llms.txt](https://fifo-docs.gitbook.io/colibri/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://fifo-docs.gitbook.io/colibri/colibri-core/signer/message-signing.md).

# SEP-53 message signing

[`LocalSigner.signMessage`](/colibri/colibri-core/signer/local-signer.md) signs UTF-8 text or `Uint8Array` using the native Stellar SDK's SEP-53 format. It does not sign the raw bytes in the same way as `sign`. Use [`LocalSigner.verifyMessage`](/colibri/colibri-core/signer/local-signer.md) or native `Keypair.verifyMessage` to verify the result.

## Sign and verify locally

No RPC connection or funded account is required. Install [`@colibri/core`](/colibri/colibri-core/overview.md) and a compatible Stellar SDK as described in [installation](/colibri/getting-started/installation.md).

```ts
import { LocalSigner } from "@colibri/core";
import { Keypair } from "npm:@stellar/stellar-sdk";

using signer = LocalSigner.generateRandom();
const message = "Approve document revision 42.";
const signature = signer.signMessage(message);
console.log(signer.verifyMessage(message, signature)); // true

const verifier = Keypair.fromPublicKey(signer.publicKey());
console.log(verifier.verifyMessage(message, signature)); // true
console.log(signature.length); // 64 bytes
```

Keep the message and public key alongside the signature. A verifier needs all three. The `using` declaration destroys the local secret handle at scope exit. Verification needs only the public key and, like `verifySignature`, still works after `signer.destroy()`. No new secret or funded account is required.

## Optional signer capability

`MessageSigner` accepts synchronous and asynchronous implementations. It is independent of [`Signer`](/colibri/colibri-core/signer.md#signer-capabilities): a message-only signer is not automatically eligible for transaction envelope signing or Soroban authorization entries. Existing signer implementations do not need to add this method unless they support SEP-53.

```ts
import { isMessageSigner } from "@colibri/core";

async function requestSignature(candidate: unknown, message: string) {
  if (!isMessageSigner(candidate)) return undefined;

  return {
    publicKey: candidate.publicKey(),
    signature: await candidate.signMessage(message),
  };
}
```

The guard checks the capability shape, not the honesty of an external signing implementation. Verify externally returned signatures before relying on them.

## Intent and failures

A signature proves control of one Ed25519 key. It does not establish that the key meets an account's multisig threshold. SEP-53 domain separation also does not define your application's expiry, nonce, audience, or replay policy. Include and validate that context according to the application's protocol.

[`LocalSigner`](/colibri/colibri-core/signer/local-signer.md) reports [`SIG_LOC_004`](/colibri/reference/errors/core-signer-local.md) when message signing follows destruction and [`SIG_LOC_005`](/colibri/reference/errors/core-signer-local.md) when the native SDK rejects message signing. The latter preserves the underlying cause without copying the input message into error metadata. Malformed verification inputs rejected by the native SDK use [`SIG_LOC_006`](/colibri/reference/errors/core-signer-local.md). A well-formed signature that does not verify returns `false`, not an error.

See the [local signer errors](/colibri/reference/errors/core-signer-local.md), [Core API](https://jsr.io/@colibri/core/doc), and [SEP-53](https://github.com/stellar/stellar-protocol/blob/master/ecosystem/sep-0053.md).