bx input sign

Create an endorsement for a transaction input.

$ bx input-sign --help

Usage: bx input-sign [-ah] [--config VALUE] [--index VALUE] [--sign_type 
VALUE] EC_PRIVATE_KEY CONTRACT [TRANSACTION]                             

Info: Create an endorsement for a transaction input.                     

Options (named):

-a [--anyone]        Modify signature hashing so that other inputs are   
                     ignored.                                            
-c [--config]        The path to the configuration settings file.        
-h [--help]          Get a description and instructions for this command.
-i [--index]         The ordinal position of the input within the        
                     transaction, defaults to zero.                      
-s [--sign_type]     A token that indicates how the transaction should be
                     hashed for signing. Options are 'all', 'none', and  
                     'single', defaults to 'all'.                        

Arguments (positional):

EC_PRIVATE_KEY       The Base16 EC private key to sign with.             
CONTRACT             The previous output script to use in signing.       
                     Multiple tokens must be quoted.                     
TRANSACTION          The Base16 transaction. If not specified the        
                     transaction is read from STDIN.

This command generates an endorsement for a transaction but does not apply it to the transaction. An endorsement is a digital signature of a input (the output of a previous transaction) which authorizes transfer of value as specified by the current transaction.

Example 1

one input, one output, standard prevout script, --sign_type all

Start with one input point and one output point as follows.

--input 7c3e880e7c93a7b01506188c36a239f70b561dfa622d0aa0d8f3b7403c94017d:0
--output 1966U1pjj15tLxPXZ19U48c99EJDkdXeqb:45000

Obtain the previous output script from the input point.

$ 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 previous output script is at transaction.outputs[0].script.

There are isolated cases where the script cannot be obtained literally from this location, however this is sufficient in more recent transactions. In cases where the script is of a typical form, as in this case, it may alternatively be inferred from the address.

The private key for the address 1JziqzXe... of the previous output will be required for signing. The value is provided here for demonstration purposes.

4ce3eb6bd06c224e3c355352a488720efc5ac9fe527a219ad35178c3cf762350

Create a new transaction, using the input and output.

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

01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c0000000000ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

Create an endorsement for the transaction, nonce, private key, previous output script and the transaction.

The following command is now invalid as a nonce [-n] is no longer allowed. Simply exclude the --nonce parameter.

$ bx input-sign -n 707e3d717925ba2e98234dd6f3a38eb5 4ce3eb6bd06c224e3c355352a488720efc5ac9fe527a219ad35178c3cf762350 "dup hash160 [c564c740c6900b93afc9f1bdaef0a9d466adf6ee] equalverify checksig" 01000000017d01943c40b7f3d8a00a2d62fa1d560bf739a2368c180615b0a7937c0e883e7c0000000000ffffffff01c8af0000000000001976a91458b7a60f11a904feef35a639b6048de8dd4d9f1c88ac00000000

30450221008f66d188c664a8088893ea4ddd9689024ea5593877753ecc1e9051ed58c15168022037109f0d06e6068b7447966f751de8474641ad2b15ec37f4a9d159b02af6817401

For the next step see Example 1 of the input-set command.

The complete scenario is detailed in How to Spend Bitcoin.