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    Author Topic: how to figure out transaction in values from addresses  (Read 1365 times)

    • earney (OP)
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    January 27, 2011, 02:09:54 AM
     #1
    how to figure out transaction IN values from addresses?  I've been looking at the output of a transaction, and I can't figure out how blockexplorer figures out the transaction in values for each bc address.

    For example,  see http://blockexplorer.com/b/104777  , the second transaction has 9 inputs with different values.   How are these derived from the raw block?

    Thanks..

  • theymos
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    January 27, 2011, 02:26:16 AM
     #2
    You need to follow the prev_out. It's not specified in the transaction. Looking at this transaction, locate output #1 in transaction b8983967c707 to get the value. It's the second "out" here. The index ("n") starts at 0.

    The difficulty of processing this by hand is one of the main reasons I wrote BBE. Previously I output all of the blocks to a file and then searched it for hashes, but I had to go back and forth dozens of times just to figure out the total value of a transaction.
    1NXYoJ5xU91Jp83XfVMHwwTUyZFK64BoAD

  • earney (OP)
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    January 27, 2011, 02:33:14 AM
     #3
    thanks..  that makes sense..  I was thinking that the values in the transaction IN added up to the values in the transaction out, but in the example I gave you, this is not the case..  Most of the time the aggregate values in tx_in was equal to the values of the tx_out..

  • Hal
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    January 27, 2011, 06:49:02 AM
     #4
    The sum of the IN values has to be greater than or equal to the sum of the OUT values. If it is greater, the difference is a transaction fee, collectable by whoever generates the block that includes this transaction.
    Hal Finney

  • theymos
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    January 27, 2011, 07:21:07 AM
     #5
    Quote from: earney on January 27, 2011, 02:33:14 AM
    thanks..  that makes sense..  I was thinking that the values in the transaction IN added up to the values in the transaction out, but in the example I gave you, this is not the case..  Most of the time the aggregate values in tx_in was equal to the values of the tx_out..

    All of the input values do add up to the output values in that block. Are you counting all of the outputs of the input transactions, perhaps?

    I forgot to answer part of your original question: you can get the actual addresses by parsing the scriptSig/scriptPubKey. My tools are useful for doing the necessary conversions:
    http://blockexplorer.com/q/hashpubkey
    http://blockexplorer.com/q/hashtoaddress
    http://blockexplorer.com/q/addresstohash

    Transactions to addresses use:
    scriptPubKey: OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG
    scriptSig: <sig> <pubKey>

    Various other less usual transactions use:
    scriptPubKey: <pubKey> OP_CHECKSIG
    scriptSig: <sig>

    You can put pubKeyHash through hashtoaddress to get the address, or you can put pubKey through hashpubkey+hashtoaddress.

    Addresses can't be easily determined for non-standard transactions such as this:
    http://blockexplorer.com/testnet/tx/802b9e557161b9bffdc2e12cc755eb4379f88014f288c2484bb39b831bb9938e#o1
    1NXYoJ5xU91Jp83XfVMHwwTUyZFK64BoAD
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