Difference between revisions of "Transaction Construction Algorithm (voting pools)"
m (→Overview) |
(Add initialize new transaction section) |
||
Line 72: | Line 72: | ||
# If the output list is non-empty, sort it by <code>outBailmentID</code> | # If the output list is non-empty, sort it by <code>outBailmentID</code> | ||
# Move both the input lists and outputs lists into separate stacks by pushing them in reverse list order. The first input and first output should be on the top of their respective stacks. | # Move both the input lists and outputs lists into separate stacks by pushing them in reverse list order. The first input and first output should be on the top of their respective stacks. | ||
+ | |||
+ | {{clear}} | ||
+ | <hr> | ||
+ | ===Initialize New Transaction=== | ||
+ | |||
+ | [[File:Transaction_Construction_Algorithm_-_Initialize New Transaction.png|175px|right|thumb]] | ||
+ | |||
+ | ====Initial Conditions==== | ||
+ | |||
+ | There are no pending transactions to in the process of being constructed, either because this is the first transaction of the algorithm or because a previous pending transaction has been moved to the finished transaction list. | ||
+ | |||
+ | ====Sequence==== | ||
+ | |||
+ | # Create a minimal transaction skeleton with a header and one change output. | ||
+ | |||
+ | After creating the transaction skeleton, and after any action which alters it, the new transaction size (bytes) and minimum required transaction fee must be recalculated. | ||
[[Category:Voting Pool Technical Specifications]] | [[Category:Voting Pool Technical Specifications]] |
Revision as of 12:37, 17 September 2014
Contents
Introduction
In order to avoid an expensive and error-prone consensus process, it is mandatory for wallets to be able to construct withdrawal transactions in a deterministic manner, assuming they are given the withdrawal requests in a deterministic order. Once this is accomplished, then it only becomes necessary for wallets to share signatures among themselves because they know they all signed the exact same bitcoin transaction.
Procedure
Overview
Initial Conditions
The getdepositscript API call has been received by the wallet, and all the arguments have been checked for errors.
Sequence
The basic flow of the procedure is:
- Gather accounting information from the API call arguments
- Validate and sort the output list
- Start a new transactions
- Add outputs to the transaction until either all outputs are added or all inputs are used.
- Make sure all generated transactions are ready for signing.
- Create a list of all signatures which the wallet is capable of generating.
- Create a status list containing the deposition of every output the caller specified.
- Return the status list and signature list to the caller.
Each step in this chart is more fully described below.
Preparation
Initial Conditions
The getdepositscript API call has been received by the wallet, and all the arguments have been checked for errors.
Sequence
- The algorithm must keep track of the next change address to be used. The initial value is supplied as the
changestart
argument. Any time a change output is allocated, the index value of the address identifier is incremented, and if a change output is remove from a transaction the index value is decremented. The final value will be returned to the caller as thenextchangestart
value in the withdrawal status list. - Prepare an empty list for holding transactions as they are constructed and before they are signed.
- Prepare an empty array to hold the transaction signatures which will be returned to the caller as the
signatures
value. - Prepare an
withdrawal status
object.roundID
: copied fromroundID
argumentnextinputstart
: nilnextchangestart
: nilfees
: 0outputs
: should contain an entry for every output passed:outBailmentID
: copied fromoutBailmentID
entry inoutputs
argumentstatus
: empty stringtransactions
: nil
Output List Initialization
Initial Conditions
The getdepositscript API call has been received by the wallet, and all the arguments have been checked for errors.
Sequence
- Pass the
inputstart
,inputstop
, anddustthreshold
parameters to the input selection algorithm to obtain an ordered list of eligible inputs. - Perform a first pass check to determine if the requested outputs exceed the size of the eligible inputs. Note that this check is only definitive in the case where the output sum is greater than the input sum. At this stage of the algorithm, the input sum exceeding the output sum does not prove that all outputs will be successfully created.
- Take the sum of both lists.
- If the sum of the outputs exceeds the sum of the inputs, remove outputs in descending size order until this is no longer true. Note this may result in the output list being an empty set.
- If the output list is non-empty, sort it by
outBailmentID
- Move both the input lists and outputs lists into separate stacks by pushing them in reverse list order. The first input and first output should be on the top of their respective stacks.
Initialize New Transaction
Initial Conditions
There are no pending transactions to in the process of being constructed, either because this is the first transaction of the algorithm or because a previous pending transaction has been moved to the finished transaction list.
Sequence
- Create a minimal transaction skeleton with a header and one change output.
After creating the transaction skeleton, and after any action which alters it, the new transaction size (bytes) and minimum required transaction fee must be recalculated.