How to Spend Bitcoin

This example is a continuation of How to Receive Bitcoin.

Create a Transaction

Look up the preceding transaction by its hash.

$ bx fetch-tx 7c3e880e7c93a7b01506188c36a239f70b561dfa622d0aa0d8f3b7403c94017d

transaction
{
    hash 7c3e880e7c93a7b01506188c36a239f70b561dfa622d0aa0d8f3b7403c94017d
    inputs
    {
        input
        {
            address 1PqLFcRyNMzsgcmT4Sd2XSVZ4XPb8CN8sj
            previous_output
            {
                hash df51c69f381a7511e95571382715cfd83c5384e9006ee7c546cfa6bb4b172346
                index 0
            }
            script "[304502206be979f1f89776e26abb40f458dc942d191d447cf3ce847d2d7e430df6b21ac4022100cade875670d71bd972f151b00544044d90a75261a9a01542968a1b36b31aea1801] [041fd7ca20852f638e82ac43b2df2ac7b38a3fec1622fb33c9f679ae909868a7e6e013429b2421a871a4e1d5d5702bea978bdd8ec399657dc6f3c0334a83de40bf]"
            sequence 4294967295
        }
    }
    lock_time 0
    outputs
    {
        output
        {
            address 1JziqzXeBPyHPeAHrG4DCDW4ASXeGGF6p6
            script "dup hash160 [c564c740c6900b93afc9f1bdaef0a9d466adf6ee] equalverify checksig"
            value 100000
        }
        output
        {
            address 18kn866ztW2Y12DkijCubQmE6xBqmJS4Gr
            script "dup hash160 [55106ed6c650e125c28f767c83ccfbc0c231fc8a] equalverify checksig"
            value 328860000
        }
    }
    version 1
}

The input for the new transaction will be transaction.outputs[0]. This input is formatted as transaction hash:index, where the index is the zero-based position of this previous output in its transaction.

7c3e880e7c93a7b01506188c36a239f70b561dfa622d0aa0d8f3b7403c94017d:0

The output for the new transaction is formatted as address:amount, where the amount is a number of satoshis. There are 100,000 satoshis available to spend, of which this transaction will spend 45% to Freenet.

1966U1pjj15tLxPXZ19U48c99EJDkdXeqb:45000

In this example the remainder will not be spent to any address. This will result in 55,000 satoshis being earned by miners as a transaction fee.

Construct the transaction from the inputs and outputs, in this case one of each.

$ bx tx-encode -i 7c3e880e7c93a7b01506188c36a239f70b561dfa622d0aa0d8f3b7403c94017d:0 -o 1966U1pjj15tLxPXZ19U48c99EJDkdXeqb:45000

01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c0000000000ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

Inspect the transaction visually.

$ bx tx-decode 01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c0000000000ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

transaction
{
    hash e433a95114dc4eb2209f7c329bad265890affb728a60ac1b967d99bbe1f25971
    inputs
    {
        input
        {
            previous_output
            {
                hash 7c3e880e7c93a7b01506188c36a239f70b561dfa622d0aa0d8f3b7403c94017d
                index 0
            }
            script ""
            sequence 4294967295
        }
    }
    lock_time 0
    outputs
    {
        output
        {
            address 1966U1pjj15tLxPXZ19U48c99EJDkdXeqb
            script "dup hash160 [58b7a60f11a904feef35a639b6048de8dd4d9f1c] equalverify checksig"
            value 45000
        }
    }
    version 1
}

Notice that transactions.inputs[0].script is empty. This means that the input has not been endorsed.

Create an endorsement for the first input 7c3e880e...:0 of the new transaction, using the private key, previous output script and the new transaction. The script is obtained from transaction.outputs[0].script in the input's transaction.

$ bx input-sign 4ce3eb6bd06c224e3c355352a488720efc5ac9fe527a219ad35178c3cf762350 "dup hash160 [c564c740c6900b93afc9f1bdaef0a9d466adf6ee] equalverify checksig" 01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c0000000000ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

30450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af6817401

Create an endorsement script using the endorsement and public key, and assign it to the first input of the transaction.

$ bx input-set "[30450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af6817401] [03e208f5403383c77d5832a268c9f71480f6e7bfbdfa44904becacfad66163ea31]" 01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c0000000000ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c000000006b4830450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af68174012103e208f5403383c77d5832a268c9f71480f6e7bfbdfa44904becacfad66163ea31ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

Validate and Broadcast the Transaction

Inspect the updated transaction visually.

$ bx tx-decode 01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c000000006b4830450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af68174012103e208f5403383c77d5832a268c9f71480f6e7bfbdfa44904becacfad66163ea31ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

transaction
{
    hash 37c9c4ee0e84c7c7924f74d92cf0779ec6e8fc4c57ebab2593562d52c61c5eb8
    inputs
    {
        input
        {
            address 1JziqzXeBPyHPeAHrG4DCDW4ASXeGGF6p6
            previous_output
            {
                hash 7c3e880e7c93a7b01506188c36a239f70b561dfa622d0aa0d8f3b7403c94017d
                index 0
            }
            script "[30450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af6817401] [03e208f5403383c77d5832a268c9f71480f6e7bfbdfa44904becacfad66163ea31]"
            sequence 4294967295
        }
    }
    lock_time 0
    outputs
    {
        output
        {
            address 1966U1pjj15tLxPXZ19U48c99EJDkdXeqb
            script "dup hash160 [58b7a60f11a904feef35a639b6048de8dd4d9f1c] equalverify checksig"
            value 45000
        }
    }
    version 1
}

Notice that the endorsement script has been applied to transaction.inputs[0].script and that transaction.hash has been updated.

Validate the endorsement of the transaction's first input, using the public key, previous output script, endorsement and transaction (optional).

$ bx input-validate 03e208f5403383c77d5832a268c9f71480f6e7bfbdfa44904becacfad66163ea31 "dup hash160 [c564c740c6900b93afc9f1bdaef0a9d466adf6ee] equalverify checksig" 30450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af6817401 01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c000000006b4830450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af68174012103e208f5403383c77d5832a268c9f71480f6e7bfbdfa44904becacfad66163ea31ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

The endorsement is valid.

Validate the transaction against the blockchain (optional).

$ bx validate-tx 01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c000000006b4830450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af68174012103e208f5403383c77d5832a268c9f71480f6e7bfbdfa44904becacfad66163ea31ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

The transaction is valid.

Broadcast the transaction to the blockchain.

$ bx send-tx 01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c000000006b4830450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af68174012103e208f5403383c77d5832a268c9f71480f6e7bfbdfa44904becacfad66163ea31ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

Sent transaction at 2014-Oct-23 00:08:49.

Confirm Spend of Bitcoin

Look up the balance of the sender address.

$ bx fetch-balance 1JziqzXeBPyHPeAHrG4DCDW4ASXeGGF6p6

balance
{
    address 1JziqzXeBPyHPeAHrG4DCDW4ASXeGGF6p6
    confirmed 0
    received 100000
    unspent 0
}

Notice that the confirmed value has been reduced by the amount spent, to zero. This is because the amount is no longer confirmed to the address. Received is not reduced by spends, and so remains unchanged. Unspent is received minus the cumulative amount spent.

View History of Spend

Look up the history for the address.

$ bx fetch-history 1JziqzXeBPyHPeAHrG4DCDW4ASXeGGF6p6

transfers
{
    transfer
    {
        received
        {
            hash 7c3e880e7c93a7b01506188c36a239f70b561dfa622d0aa0d8f3b7403c94017d
            height 326392
            index 0
        }
        spent
        {
            hash 37c9c4ee0e84c7c7924f74d92cf0779ec6e8fc4c57ebab2593562d52c61c5eb8
            height 326581
            index 0
        }
        value 100000
    }
}

The amount previously received has been spent.

Determine Spend Confirmation Level

Look up the current blockchain height.

$ bx fetch-height

326590

Using transfers[0].spent.height, there are currently 326590 - 326581 = 9 confirmations for the transaction.

View the spend transaction on blockchain.info.