CubeSigner Snap

This package provides an interface to CubeSigner's remote services via the MetaMasks's JSON-RPC snap API.

CubeSigner is a hardware-backed, non-custodial platform for securely managing cryptographic keys. The CubeSigner Snap uses the CubeSigner TypeScript SDK to let your MetaMask users sign transactions on EVM-based chains like Ethereum, Avalanche, and Polygon, and on non-EVM chains like Bitcoin and Solana.

CubeSigner background

The Cubist team built CubeSigner to address the key security vs key availability tradeoff: right now, many teams are forced to keep keys available in memory and therefore exposed to attackers, or try to keep keys safe—usually only at rest—at serious latency and engineering cost. CubeSigner addresses this problem by giving developers low-latency access to hardware-backed key generation and signing. During each of these operations, CubeSigner safeguards their users' keys in HSM-sealed Nitro Enclaves—combining cold wallet security with hot wallet speed and simplicity.

Right now, the CubeSigner Snap supports signing for EVM chains like Ethereum and Avalanche, and non-EVM chains Bitcoin and Solana. Support for more chains and more features is in the works!

JSON-RPC methods

login

Prompts the user to log into CubeSigner. A dApp or snap can automatically log the user in by providing the user's API session token (which they can get by authenticating the user server-side); alternatively they can ask the user to input their secret API session token.

Warning The API session token is sensitive and can be used to sign with (some of) your keys. Do NOT share it or paste it anywhere except the CubeSigner Snap dialog.

Example (with token)

await window.ethereum.request<boolean>({
  method: "wallet_invokeSnap",
  params: {
    snapId: defaultSnapId,
    request: {
      method: "login",
      params: { token_base64: "ewog...Q===" },
    },
  },
});

Example (without token)

await window.ethereum.request<boolean>({
  method: "wallet_invokeSnap",
  params: { snapId: defaultSnapId, request: { method: "login" } },
});

logout

Asks the user for confirmation, then logs out of CubeSigner. If successful, notifies the user.

Example

await window.ethereum.request({
  method: "wallet_invokeSnap",
  params: { snapId: defaultSnapId, request: { method: "logout" } },
});

get_keys

Returns all keys accessible from the current session.

Returns

An array of objects, each of which containing:

• id: string - the unique key identifier
• enabled: boolean - whether the key is enabled
• type: KeyType - key type (e.g., "SecpEthAddr", "SecpBtc", "BlsPub", etc.)
• materialId: string - a unique identifier specific to the type of key, such as a public key or an Ethereum address
• publicKey: string - hex-encoded, serialized public key (the format used depends on the key type)
• owner: string - the unique identifier of user who owns the key

Example

const keys = (await window.ethereum.request<Key[]>({
  method: "wallet_invokeSnap",
  params: { snapId: defaultSnapId, request: { method: "get_keys" } },
})) as Key[];

keys.forEach((key) => console.log(key.id));

sign_blob

Asks the user for confirmation, then proceeds to sign a raw blob.

Parameters

• keyId: string - the identifier of the key to use for signing (corresponds to the KeyInfo.key_id property)
• body: BlobSignRequest - the request object containing:
  • message_base64: string - the blob to sign, encoded as a base64 string

Returns

An object containing the signature:

• signature: string - the signature, encoded as a hex string

Example

const sig = (await window.ethereum.request<BlobSignResponse>({
  method: "wallet_invokeSnap",
  params: {
    snapId: defaultSnapId,
    request: {
      method: "sign_blob",
      params: {
        keyId: "Key#...",
        body: { message_base64: "L1kE9g59xD3fzYQQSR7340BwU9fGrP6EMfIFcyX/YBc=" },
      },
    },
  },
})) as BlobSignResponse;

console.log(sig.signature);

sign_evm

Asks the user for confirmation, then proceeds to sign an EVM transaction.

Parameters

• pubkey: string - the material ID of the key to use for signing (corresponds to the KeyInfo.material_id property)
• body: Eth1SignRequest - the request object containing:
  • chain_id: number - the ID of the chain
  • tx - unsigned transaction

Returns

An object containing the signature:

• rlp_signed_tx: string - hex-encoded RLP encoding of the transaction and its signature

Example

const sig = (await window.ethereum.request<Eth1SignResponse>({
  method: "wallet_invokeSnap",
  params: {
    snapId: defaultSnapId,
    request: {
      method: "sign_evm",
      params: {
        pubkey: "0x...",
        body: {
          chain_id: 1,
          tx: { ... }
        }
      }
    }
  },
})) as Eth1SignResponse;

console.log(sig.rlp_signed_tx);

sign_solana

Asks the user for confirmation, then proceeds to sign a Solana transaction.

Parameters

• pubkey: string - the material ID of the key to use for signing (corresponds to the KeyInfo.material_id property)
• body: SolanaSignRequest - the request object containing
  • message - Solana message to sign

Returns

A SolanaSignResponse object containing the signature:

• signature: string - hex-encoded signature

Example

const sig = (await window.ethereum.request<SolanaSignResponse>({
  method: "wallet_invokeSnap",
  params: {
    snapId: defaultSnapId,
    request: {
      method: "sign_solana",
      params: {
        pubkey: "Solana_...",
        body: {
          message: { ... }
        }
      }
    }
  },
})) as SolanaSignResponse;

console.log(sig.signature);

sign_btc

Asks the user for confirmation, then proceeds to sign a Bitcoin transaction.

• pubkey: string - the material ID of the key to use for signing (corresponds to the KeyInfo.material_id property)
• body: BtcSignRequest - the request object

Returns

A BtcSignResponse object containing the signature:

• signature: string - the hex-encoded signature in DER format

Example

const sig = (await window.ethereum.request<BtcSignResponse>({
  method: "wallet_invokeSnap",
  params: {
    snapId: defaultSnapId,
    request: {
      method: "sign_btc",
      params: {
        pubkey: "bc1...",
        body: {
          sig_kind: {
            Segwit: {
              input_index: 0,
              script_code: "0x76a91479091972186c449eb1ded22b78e40d009bdf008988ac",
              value: 1_000_000,
              sighash_type: "All",
            },
            tx: {
              version: 1,
              lock_time: 1170,
              input: [
                {
                  previous_output:
                    "77541aeb3c4dac9260b68f74f44c973081a9d4cb2ebe8038b2d70faa201b6bdb:1",
                  script_sig: "",
                  sequence: 4294967294,
                  witness: [],
                },
              ],
              output: [
                {
                  value: 199996600,
                  script_pubkey: "76a914a457b684d7f0d539a46a45bbc043f35b59d0d96388ac",
                },
                {
                  value: 800000000,
                  script_pubkey: "76a914fd270b1ee6abcaea97fea7ad0402e8bd8ad6d77c88ac",
                },
              ],
            },
          },
        },
      },
    },
  },
})) as BtcSignResponse;

console.log(sig.signature);