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Create Signature for Ethereum Blockchain

Ethereum has a dedicated signature format which allows to recover the public-key and subsequently the address based on the signature. This format reduces the payload-size of the Transaction and improves speed, dedicated for the Ethereum Blockchain.

The followin example creates a SKA-Key, extracts the wallets address and produces a valid signature.

Create Key​

Creating a Key on the HSM, which is not destroyable (e.g. cannot be deleted), and uses SmartKeyAttributes.

ADDRESS GENERATION

If your subscription Type includes SmartKeyAttributes, the HSM is generating the Wallet-Address for you, by specifying in the request below.

    "addressFormat": {
        "format": "ETH"
    },

If you do not have a SmartKeyAttributes subscription, you must remove the policy and the addressFormat from the request below. Be careful, you have to generate the address by yourself!

{
    "label": "ether_Transaction_signing_key",
    "algorithm": "EC",
    "curveOid": "1.3.132.0.10",
    "addressFormat": {
        "format": "ETH"
    },
    "attributes": {
        "decrypt": false,
        "sign": true,
        "unwrap": false,
        "destroyable": false,
        "modifiable": true,
        "derive": true,
        "bip32": true
    },
    "policy": {
        "keyStatus": {
            "blocked": false
        }
    }
}

The SKA-Policy above is empty, which means the request does not need any approvals. For a more comprehensive policy, checkout this sample.

Extract Address​

With an SKA License you have three possibilities to get the wallet-address.

1. Create Key Response​

Fetch the address from the Create Key Response

Response:

    "addressTruncated": {
      "address": "B476FABAAB46013A7DB5193378BABE674166CE61",
      "format": "ETH"
    },

2. Get Attributes​

Fetch the address from the Get Key Attributes Response

Response:

    "addressTruncated": {
      "address": "B476FABAAB46013A7DB5193378BABE674166CE61",
      "format": "ETH"
    },

3. Get the address​

Fetch the address from the Get Address Response

Response:

{
  "address": "tHb6uqtGATp9tRkzeLq+Z0FmzmE="
}
Tip

For method 2, 3 you can use temporary key derivation to generate addresses and signatures withouth filling the HSM-Storage.

Sign a payload​

tip

Use the Generate a signature with the request-body below to sign a transaction with the HSM-backed private key.

The singnatureType tells TSB to produce a valid signature for the Ethereum Blockchain. If the Type ETH is specified the signature must be KECCAK256_WITH_ECDSA as the ethereum blockchain uses Keccak256 as default.

{
  "signRequest": {
    "payload": "YXNk",
    "payloadType": "UNSPECIFIED",
    "signKeyName": "ether_Transaction_signing_key",
    "signatureType": "ETH",
    "signatureAlgorithm": "KECCAK256_WITH_ECDSA"
  }
}

Verify Signature​

The signature can be verified with the etherscans verification tool:

https://etherscan.io/verifiedSignatures# (make sure you have base64 decoded the signature result)

Etherscan: Verify Success