Validate the tosign data returned by BlockCypher

gistfile1.sh

# create the transaction
$ curl -d '{"inputs": [{"addresses": ["mtWg6ccLiZWw2Et7E5UqmHsYgrAi5wqiov"]}],
            "outputs":[{"addresses": ["mzUqjgiGc3Mqh5zMiP5vXDNd7Hwx3K1xCU"], "value": 25000}]}' \
            https://api.blockcypher.com/v1/btc/test3/txs/new?includeToSignTx=true
{
  "tx": {
    "block_height": -1,
    "hash": "568acff13300b471d384e16a1a6d449be704e97b819f051dc4f1fb246726e471",
    "addresses": [
      "mzUqjgiGc3Mqh5zMiP5vXDNd7Hwx3K1xCU",
      "mtWg6ccLiZWw2Et7E5UqmHsYgrAi5wqiov"
    ],
    "total": 23477984,
    "fees": 12000,
    "size": 119,
    "preference": "high",
    "relayed_by": "169.53.156.231",
    "received": "2015-04-30T18:22:37.060105514Z",
    "ver": 1,
    "lock_time": 0,
    "double_spend": false,
    "vin_sz": 1,
    "vout_sz": 2,
    "confirmations": 0,
    "inputs": [
      {
        "prev_hash": "911ac2cd4e3c18fdb752a0d59e5ad220722b718cb80d53d5a6cae9c74d026efc",
        "output_index": 1,
        "script": "",
        "output_value": 23489984,
        "sequence": 4294967295,
        "addresses": [
          "mtWg6ccLiZWw2Et7E5UqmHsYgrAi5wqiov"
        ],
        "script_type": "",
        "age": 2870
      }
    ],
    "outputs": [
      {
        "value": 25000,
        "script": "76a914d004156436b38ef464b01286cdc9c4b36c99c68788ac",
        "addresses": [
          "mzUqjgiGc3Mqh5zMiP5vXDNd7Hwx3K1xCU"
        ],
        "script_type": "pay-to-pubkey-hash"
      },
      {
        "value": 23452984,
        "script": "76a9148e8c1d4adef86c11154fd04b5012306715fd4baf88ac",
        "addresses": [
          "mtWg6ccLiZWw2Et7E5UqmHsYgrAi5wqiov"
        ],
        "script_type": "pay-to-pubkey-hash"
      }
    ]
  },
  "tosign_tx": [
   "0100000001fc6e024dc7e9caa6d5530db88c712b7220d25a9ed5a052b7fd183c4ecdc21a91010000001976a9148e8c1d4adef86c11154fd04b5012306715fd4baf88acffffffff02a8610000000000001976a914d004156436b38ef464b01286cdc9c4b36c99c68788ac38dd6501000000001976a9148e8c1d4adef86c11154fd04b5012306715fd4baf88ac0000000001000000"
  ],
  "tosign": [
    "b365bef9aae17e0d35963217d65915a2a00bc782f1bb1be5061a18d92063309e"
  ]
}

# decode the tosign_tx data returned to validate the transaction data matches the required inputs and outputs
$ curl -d '{"tx": "0100000001fc6e024dc7e9caa6d5530db88c712b7220d25a9ed5a052b7fd183c4ecdc21a91010000001976a9148e8c1d4adef86c11154fd04b5012306715fd4baf88acffffffff02a8610000000000001976a914d004156436b38ef464b01286cdc9c4b36c99c68788ac38dd6501000000001976a9148e8c1d4adef86c11154fd04b5012306715fd4baf88ac0000000001000000"}' https://api.blockcypher.com/v1/btc/test3/txs/decode
{
  "block_height": -1,
  "hash": "855d69a6b56bf159d84efd6e0243f8d45d429df482560cae619a6f552ab43a0b",
  "addresses": [
    "mtWg6ccLiZWw2Et7E5UqmHsYgrAi5wqiov",
    "mzUqjgiGc3Mqh5zMiP5vXDNd7Hwx3K1xCU"
  ],
  "total": 23477984,
  "fees": 12000,
  "size": 144,
  "preference": "high",
  "relayed_by": "169.53.156.231",
  "received": "2015-04-30T18:44:08.591995605Z",
  "ver": 1,
  "lock_time": 0,
  "double_spend": false,
  "vin_sz": 1,
  "vout_sz": 2,
  "confirmations": 0,
  "inputs": [
    {
      "prev_hash": "911ac2cd4e3c18fdb752a0d59e5ad220722b718cb80d53d5a6cae9c74d026efc",
      "output_index": 1,
      "script": "76a9148e8c1d4adef86c11154fd04b5012306715fd4baf88ac",
      "output_value": 23489984,
      "sequence": 4294967295,
      "addresses": [
        "mtWg6ccLiZWw2Et7E5UqmHsYgrAi5wqiov"
      ],
      "script_type": "pay-to-pubkey-hash",
      "age": 2893
    }
  ],
  "outputs": [
    {
      "value": 25000,
      "script": "76a914d004156436b38ef464b01286cdc9c4b36c99c68788ac",
      "addresses": [
        "mzUqjgiGc3Mqh5zMiP5vXDNd7Hwx3K1xCU"
      ],
      "script_type": "pay-to-pubkey-hash"
    },
    {
      "value": 23452984,
      "script": "76a9148e8c1d4adef86c11154fd04b5012306715fd4baf88ac",
      "addresses": [
        "mtWg6ccLiZWw2Et7E5UqmHsYgrAi5wqiov"
      ],
      "script_type": "pay-to-pubkey-hash"
    }
  ]
}

# validate that tosign is equal to tosign_tx after 2 rounds of sha256 hashing
$ echo -n "0100000001fc6e024dc7e9caa6d5530db88c712b7220d25a9ed5a052b7fd183c4ecdc21a9101000001976a9148e8c1d4adef86c11154fd04b5012306715fd4baf88acffffffff02a8610000000000001976a914d004156436b38ef464b01286cdc9c4b36c99c68788ac38dd6501000000001976a9148e8c1d4adef86c11154fd04b5012306715fd4baf88ac0000000001000000" | xxd -r -p | sha256sum -b
f80804283c023d50bdf3ba6a4f938dc2e65767b8aa55414ea6aae9ef410a55a6 *-
$ echo -n "f80804283c023d50bdf3ba6a4f938dc2e65767b8aa55414ea6aae9ef410a55a6" | xxd -r -p | sha256sum -b
b365bef9aae17e0d35963217d65915a2a00bc782f1bb1be5061a18d92063309e *-