bitcoin-operations-draft

btc_input_data_operation (Same as bitcoin_issue_operation in Sidechain)

This operation creates an object that stores the information about deposits for their further approval. Some minor changes will be required in its implementation i.e. the operation has to be signed by the active SONs holding more than 2/3rd of the votes.

This operation contains the following fields:

Type	Name	Description
asset	fee	transaction fee for the operation
account_id_type	payer	SON account
vector<info_for_vin>	info_for_vins	a vector of vins
string	btc_block_hash	hash of a block on the side of BTC
uint64_t	estimated_feerate	estimate fee for Bitcoin transaction

This operation is handled as follows:

1) Index is searched by id for vins same as the vin that is being added ( hash( string(hash_of_trx) + string(n_vout) ) ). 2) Id is calculated by the evaluator, since if it is passed in an operation, a potential attack vector opens: a valid ID for a different vin could be used to get approvals on another vin. 3) If nothing was found, a new btc_input_data_object object is created, storing the number of active SON members. son_id of the SON that sent the operation to set is also recorded in order to check confirmations by other SONs. 4) If set.size() > (2/3 + 1) * active_son_members_amount, btc_input_data_object object is considered confirmed (the consensus part). 5) Estimated fee index is searched for btc_fee_data_object by ID ( hash( string(btc_block_hash) ) ). 6) If no object was found, we create a btc_fee_data_object object, storing the number of active SON members. 7) Estimate fee map (key=son_id, value=fee) is checked for records about operation sender. If there is a record, handling stops. 8) If there are no records found in step 7, new information is recorded to the map. 9) If map.size() > (2/3 + 1) * active_son_members_amount, btc_fee_data_object is considered confirmed (the consensus part).

btc_withrawal_operation (Same as withdraw_pBTC_operation in the existing Sidechain feature)

This operation creates an object with information about a BTC withdrawal (btc_withdrawal_object). Some minor changes will be required in its implementation i.e. the operation has to be signed by the active SONs holding more than 2/3rd of the votes.

The fields are as follows:

Type	Name	Description
asset	fee	fee for the transaction on PeerPlays blockchain
account_id_type	payer	id of the PeerPlays account that initiates the withdrawal
string	data	bitcoin address, to which BTC is being withdrawn
uint64_t	amount	the amount of withdrawal in satoshis

This operation is handled as follows:

1) Validation is performed to make sure that the withdrawing PeerPlays account has enough pBTC for the withdrawal amount + fees (withdrawal amount + fee for son members + fee for Bitcoin transaction). 2) btc_withdrawal_object is created. It contains the following information: ID of the withdrawing account (account_id_type), Bitcoin address to withdraw to (string), amount of withdrawal in satoshis (uint64_t), used flag that indicates whether this object has been used (bool). 3) The amount from step 1 is burnt from the withdrawing user's balance 4) Confirmed objects are processed once every N block on PeerPlays (where N is a constant specified in the protocol. An example of N is 300 - since average blockTime on Bitcoin is ~10 minutes, and ~2 seconds on PeerPlays), which allows to minimize the tx fees by placing multiple withdrawals into one transaction. 5) On the node accepting a PeerPlays block a check is performed on its number (block_number % N == 0). If block_number = N, a btc_transaction_object, that contains a Bitcoin transaction. If inputs и withdrawals exceed the size of a Bitcoin transaction, another object is created containing a transaction that depends on the previous one. 6) On block acceptance an index storing the objects with btc_tx is checked. If it cointains an unsigned transaction, a signal for creating a son_member signature is emitted. 7) A Bitcoin transaction is emitted to Bitcoin blockchain once the object receives the required number of signatures.

btc_transaction_sign_operation (Same as btc_transaction_sign_operation in the existing Sidechain feature)

This operation serves to sign Bitcoin transactions by SONs. Some minor changes will be required in its implementation i.e. the operation has to be signed by the active SONs holding more than 2/3rd of the votes. It contains the following fields:

Type	Name	Description
asset	fee	fee for the transaction on PeerPlays blockchain
account_id_type	payer	SON account that pays the fee
vector<vector>	signatures	Signatures for vins

The process for signing a transaction is as follows: 1) When a signal from database::apply_block is called to create a signature for a Bitcoin transaction, a method from btc_sidechain_service is called. 2) btc_transaction_sign_operation is created storing the signature, and is broadcast on PeerPlays blockchain. evaluator class for this operation records btc_transaction_object of the signature, and, when the required number of signatures is collected ((2 / 3 + 1) * son_members_amount), sorts them in accordance with redeem script. The sorting is required since the keys in multisig script are handled in pre-defined order, and it is required that signatures are sorted in the same order (key - signature).