Where are transaction signatures beside the scriptSig?

Question

To spend a UTXO, we need to sign it (have the scriptSig). Then we can spend that UTXO to any address we want, which it wasn't included in the signature we produced for unlocking the UTXO. So we should provide another signature to express our intention that we want to spend to this specific output[s]. Is this right? When I try to observe a transaction using bitcoin-cli I don't see any signature for the whole transaction.

# bitcoin-cli -regtest  gettransaction 58abd7cda78c3140383bbf950420171b6e630f784d33392b968d9db7ea7d6c25
{
  "amount": 0.00000000,
  "fee": -0.00002820,
  "confirmations": 0,
  "trusted": true,
  "txid": "58abd7cda78c3140383bbf950420171b6e630f784d33392b968d9db7ea7d6c25",
  "wtxid": "40ef85dd2f2f54254f13c179b8fa18a247d493fd3f583ce4c0932754dfad89ed",
  "walletconflicts": [
  ],
  "time": 1683793800,
  "timereceived": 1683793800,
  "bip125-replaceable": "yes",
  "details": [
    {
      "address": "bcrt1qt3lltc5dx4gwmlcd0uqxkl85xrv7msfkmjyjts",
      "category": "send",
      "amount": -12.34500000,
      "label": "",
      "vout": 1,
      "fee": -0.00002820,
      "abandoned": false
    },
    {
      "address": "bcrt1qt3lltc5dx4gwmlcd0uqxkl85xrv7msfkmjyjts",
      "parent_descs": [
        "wpkh(tpubD6NzVbkrYhZ4YcCHtvXU4pzZAcAH2eet5KJvzXoxvjGGdBzAepGK3keAQS8pv1pQYyM4VdudgnmaDr4YXXemgdtKh4Yh5cbG3uCHV8q7Aub/84'/1'/0'/0/*)#h8mhq3zh"
      ],
      "category": "receive",
      "amount": 12.34500000,
      "label": "",
      "vout": 1
    }
  ],
  "hex": "020000000001016c34e216d1f6821d91bc42e377290a7d30968da52c88678ecc2b47757ee8333d0000000000fdffffff025ced70e000000000160014bde66028298d70a6ec1bbb8e9c0a87f40db4c8d9a0f99449000000001600145c7ff5e28d3550edff0d7f006b7cf430d9edc136024730440220045193a2e68e19f815741f1b6338fc8c52d6808b5b63e387f1ef411e509bf78002207ab592b6d5bd9b47a6c0b4cdad119b05a43cb8274ecb5bffd16de881ecaa005d0121024bad563526f76fdbb915e7af18aed4ff8c48cf853440c2fda07076078d1c1346cb000000"
}

# bitcoin-cli -regtest getblock 757783d237294945126b5966a46ddaf44e3ce04b0cd5bba726dc441dbadbb5be 2
{
  "hash": "757783d237294945126b5966a46ddaf44e3ce04b0cd5bba726dc441dbadbb5be",
  "confirmations": 1,
  "height": 204,
  "version": 805306368,
  "versionHex": "30000000",
  "merkleroot": "b2de6af12b36d32bad5f358cabab6d5dee5d976568a5039f5fd7273ee0905afa",
  "time": 1683795140,
  "mediantime": 1683793734,
  "nonce": 0,
  "bits": "207fffff",
  "difficulty": 4.656542373906925e-10,
  "chainwork": "000000000000000000000000000000000000000000000000000000000000019a",
  "nTx": 2,
  "previousblockhash": "2b6ce151ace43623880979d4b137e14865e07d59195b242fa273b13dd6b59c13",
  "strippedsize": 327,
  "size": 472,
  "weight": 1453,
  "tx": [
    {
      "txid": "860c1c07d52b2709e717780f1c91845ca338199da9eead89069ff458dc59e509",
      "hash": "957b22a4ce7df3e0b05bdf216f9ca14bd8f1bcae3ebc68870ef92035af941fe4",
      "version": 2,
      "size": 169,
      "vsize": 142,
      "weight": 568,
      "locktime": 0,
      "vin": [
        {
          "coinbase": "02cc0000",
          "txinwitness": [
            "0000000000000000000000000000000000000000000000000000000000000000"
          ],
          "sequence": 4294967295
        }
      ],
      "vout": [
        {
          "value": 25.00002820,
          "n": 0,
          "scriptPubKey": {
            "asm": "0 798fcf4772e285431c55ce67f2e0333f11d03f8b",
            "desc": "addr(bcrt1q0x8u73mju2z5x8z4eenl9cpn8ugaq0utj7n0jd)#nxvln3g4",
            "hex": "0014798fcf4772e285431c55ce67f2e0333f11d03f8b",
            "address": "bcrt1q0x8u73mju2z5x8z4eenl9cpn8ugaq0utj7n0jd",
            "type": "witness_v0_keyhash"
          }
        },
        {
          "value": 0.00000000,
          "n": 1,


      "weight": 561,
      "locktime": 203,
      "vin": [
        {
          "txid": "3d33e87e75472bcc8e67882ca58d96307d0a2977e342bc911d82f6d116e2346c",
          "vout": 0,
          "scriptSig": {
            "asm": "",
            "hex": ""
          },
          "txinwitness": [
            "30440220045193a2e68e19f815741f1b6338fc8c52d6808b5b63e387f1ef411e509bf78002207ab592b6d5bd9b47a6c0b4cdad119b05a43cb8274ecb5bffd16de881ecaa005d01",
            "024bad563526f76fdbb915e7af18aed4ff8c48cf853440c2fda07076078d1c1346"
          ],
          "sequence": 4294967293
        }
      ],
      "vout": [
        {
          "value": 37.65497180,
          "n": 0,
          "scriptPubKey": {
            "asm": "0 bde66028298d70a6ec1bbb8e9c0a87f40db4c8d9",
            "desc": "addr(bcrt1qhhnxq2pf34c2dmqmhw8fcz587sxmfjxef2k5ag)#x0qwx2ck",
            "hex": "0014bde66028298d70a6ec1bbb8e9c0a87f40db4c8d9",
            "address": "bcrt1qhhnxq2pf34c2dmqmhw8fcz587sxmfjxef2k5ag",
            "type": "witness_v0_keyhash"
          }
        },
        {
          "value": 12.34500000,
          "n": 1,
          "scriptPubKey": {
            "asm": "0 5c7ff5e28d3550edff0d7f006b7cf430d9edc136",
            "desc": "addr(bcrt1qt3lltc5dx4gwmlcd0uqxkl85xrv7msfkmjyjts)#f706enkn",
            "hex": "00145c7ff5e28d3550edff0d7f006b7cf430d9edc136",
            "address": "bcrt1qt3lltc5dx4gwmlcd0uqxkl85xrv7msfkmjyjts",
            "type": "witness_v0_keyhash"
          }
        }
      ],
      "fee": 0.00002820,
      "hex": "020000000001016c34e216d1f6821d91bc42e377290a7d30968da52c88678ecc2b47757ee8333d0000000000fdffffff025ced70e000000000160014bde66028298d70a6ec1bbb8e9c0a87f40db4c8d9a0f99449000000001600145c7ff5e28d3550edff0d7f006b7cf430d9edc136024730440220045193a2e68e19f815741f1b6338fc8c52d6808b5b63e387f1ef411e509bf78002207ab592b6d5bd9b47a6c0b4cdad119b05a43cb8274ecb5bffd16de881ecaa005d0121024bad563526f76fdbb915e7af18aed4ff8c48cf853440c2fda07076078d1c1346cb000000"
    }
  ]
}

score 3 · Accepted Answer · answered May 11 '23 at 09:18

3

Modern transaction, since SegWit, include signatures in a new field: the witness. The witness replaces the scriptSig. You can see in your example how txinwitness contains a public key and a signature for the single input of your transaction.

Related: "What is the Witness and what data does it contain?".

answered May 11 '23 at 09:18

Antoine Poinsot

5,881
2
11
28

What about legacy transactions? – Amir reza Riahi May 11 '23 at 12:52
2

@AmirrezaRiahi In pre-segwit transaction inputs, the signature data is in the `scriptSig`. In segwit transaction inputs, the signature data is in the witness. – Pieter Wuille May 11 '23 at 15:01
@PieterWuille Thanks for clarification – Amir reza Riahi May 11 '23 at 15:09
The `scriptSig` is a per input entity, right? not for a whole transaction. My question is about the signature of the whole transaction. – Amir reza Riahi May 11 '23 at 15:11
1

There is no such thing as a signature for the whole transaction. Signatutes are always per input. – Pieter Wuille May 11 '23 at 15:17
@PieterWuille So how the input is protected against being used to another output? One can put a signed input and create another transaction and use that input in it. – Amir reza Riahi May 11 '23 at 15:36
1

@AmirrezaRiahi Every signature (typically) signs *all* inputs (including itself) and *all* outputs. It just doesn't sign the *signatures* in those inputs. – Pieter Wuille May 11 '23 at 16:17

Where are transaction signatures beside the scriptSig?

1 Answers1