construction/combine - Cardano

Example code for the construction/combine JSON_RPC method. Complete guide on how to use construction/combineJSON_RPC in GetBlock Web3 documentation.

This endpoint combines an unsigned transaction with its signatures to produce a signed transaction. It is an offline step in the construction flow.

Parameters

The request body is a JSON object with the following fields.

Field	Type	Required	Description
network_identifier	object	Yes	The network to construct for
unsigned_transaction	string	Yes	The unsigned transaction CBOR hex
signatures	array	Yes	The signatures produced for the payloads

Request

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/construction/combine' \
--header 'Content-Type: application/json' \
--data-raw '{
    "network_identifier": {
        "blockchain": "cardano",
        "network": "mainnet"
    },
    "unsigned_transaction": "a400818258200e...unsigned-cbor...",
    "signatures": [
        {
            "signing_payload": {
                "account_identifier": {
                    "address": "addr1qxy2lpan99fcnhhyzr8w8qk4dqz4mp7g6b8h3r2v5c9d0e1f2g3h4j5k6l7m8n9p0q"
                },
                "hex_bytes": "3e6f2d8c...signing-payload"
            },
            "public_key": {
                "hex_bytes": "b3c2a1d0e9f8...ed25519-public-key-hex",
                "curve_type": "edwards25519"
            },
            "signature_type": "ed25519",
            "hex_bytes": "a1b2c3...signature"
        }
    ]
}'

JavaScript

const response = await fetch(
    'https://go.getblock.io/<ACCESS-TOKEN>/construction/combine',
    {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({"network_identifier": {"blockchain": "cardano", "network": "mainnet"}, "unsigned_transaction": "a400818258200e...unsigned-cbor...", "signatures": [{"signing_payload": {"account_identifier": {"address": "addr1qxy2lpan99fcnhhyzr8w8qk4dqz4mp7g6b8h3r2v5c9d0e1f2g3h4j5k6l7m8n9p0q"}, "hex_bytes": "3e6f2d8c...signing-payload"}, "public_key": {"hex_bytes": "b3c2a1d0e9f8...ed25519-public-key-hex", "curve_type": "edwards25519"}, "signature_type": "ed25519", "hex_bytes": "a1b2c3...signature"}]})
    }
);
console.log(await response.json());

Python

import requests

response = requests.post(
    'https://go.getblock.io/<ACCESS-TOKEN>/construction/combine',
    headers={'Content-Type': 'application/json'},
    json={"network_identifier": {"blockchain": "cardano", "network": "mainnet"}, "unsigned_transaction": "a400818258200e...unsigned-cbor...", "signatures": [{"signing_payload": {"account_identifier": {"address": "addr1qxy2lpan99fcnhhyzr8w8qk4dqz4mp7g6b8h3r2v5c9d0e1f2g3h4j5k6l7m8n9p0q"}, "hex_bytes": "3e6f2d8c...signing-payload"}, "public_key": {"hex_bytes": "b3c2a1d0e9f8...ed25519-public-key-hex", "curve_type": "edwards25519"}, "signature_type": "ed25519", "hex_bytes": "a1b2c3...signature"}]}
)

print(response.json())

Response

{
    "signed_transaction": "84a400818258200e...signed-cbor..."
}

Response Parameters

Field	Type	Description
signed_transaction	string	The signed transaction in CBOR hex

Use Cases

• Signature Assembly: Attach signatures to an unsigned transaction

• Offline Signing: Combine signatures produced on an air-gapped device

• Multi-Signature: Assemble signatures from several signers

• Construction Flow: Advance to the hash and submit steps

Error Handling

Error Code	Message	Description
1	Invalid request	A required construction field is missing or malformed
6	Transaction decode failed	The supplied transaction could not be decoded
14	Invalid signature	A supplied signature is malformed or does not match
5	Internal error	The node failed to process the construction step