Transaction

A transaction is a signed section of data that is broadcast to the network and collected into blocks. It typically references previous transaction(s) and dedicates a certain number of novacoins from it to one or more new public key(s).

Currently there are a few transaction types possible.

User operation

This transactions are typically used to redeem novacoins from unspent inputs. It generally references unspent input(s) and creates a new output(s) with specified value(s) an destination(s).

Coinbase

Coinbase have a single input, and this input has a "coinbase" parameter instead of a scriptSig. The data in "coinbase" can be anything; it isn't used. Novacoin puts the current compact-format target and the arbitrary-precision "extraNonce" number there, which increments every time the Nonce field in the block header overflows. The extranonce contributes to enlarge the domain for the proof of work function.

This transactions are used to reward the proof-of-work miners. Proof-of-stake blocks have the coinbase transaction too, but with empty output.

Coinstake

This transactions are used to provide a suitable proof for proof-of-stake block header. This type is similar to user transactions, but with some differences.

• First output must be empty;
• First input of this transaction is required to satisfy a current proof-of-stake difficulty.
• It's allowed to generate new coins through paying a negative fee.
• A destination of the second output must be Pay-to-Pubkey (described later).

General format of a transaction

Field	Type	sizeof	Description
Version	unsigned int	4	Currently 1
Timestamp	unsigned int	4	Transaction timestamp
Inputs count	variable int	1 - 9	-
Inputs array	TxIn[]	inputs set size	Inputs array or coinbase property
Outputs count	variable int	1 - 9	-
Outputs array	TxOut[]	outputs set size	Array of output structures
Lock time	unsigned int	4	block height or timestamp when transaction is final

Input format

An input is a reference to an output in a different transaction. Multiple inputs are often listed in a transaction. The values of the referenced outputs are added up, and the total is usable in the outputs of this transaction.

Field	Type	sizeof	Description
txid	unsigned char[]	32	ID of previous transaction
n	unsigned int	4	Number indexing an output of the to-be-consumed transaction
scriptSigLength	variable int	1-9	scriptSig length
scriptSig	unsigned char[]	-	first half of script, signatures for the scriptPubKey
nSequence	unsigned int	4	Transaction variant number, irrelevant if nLockTime isn't specified. 0xffffffff by default, see this link for a detailed explanation.

Output format

An output contains instructions for sending novacoins. Value is the number of Satoshi (1 NVC = 1,000,000 Satoshi) that this output will be worth when claimed.

Field	Type	sizeof	Description
nValue	unsigned long int	8	the number of Satoshis(NVC/10^6) to be transfered
scriptPubKeyLength	variable int	1-9	scriptPubKey length
scriptPubKey	unsigned char[]	-	second half of script, spending instructions

Destinations

There are three destination types allowed for user and coinbase transactions:

• Public key (Pay-to-Pubkey);
• Public key hash (Pay-to-PubkeyHash);
• Script hash (Pay-to-ScriptHash);
• Empty destination;
• Non-standard script.

Pay-to-Pubkey

scriptPubKey: [pubKey] OP_CHECKSIG
scriptSig: [sig]

Pay-to-PubkeyHash

scriptPubKey: OP_DUP OP_HASH160 [pubKeyHash] OP_EQUALVERIFY OP_CHECKSIG
scriptSig: [sig] [pubKey]

Pay-to-ScriptHash

Send to script hash:

scriptPubKey: OP_HASH160 [20-byte-hash of {[pubkey] OP_CHECKSIG} ] OP_EQUAL
scriptSig: <depending on inputs type>

Redeem example:

scriptPubKey: OP_HASH160 [20-byte-hash of {[pubkey] OP_CHECKSIG} ] OP_EQUAL
scriptSig: [signature] {[pubkey] OP_CHECKSIG}

Empty destinations

scriptPubKey: (empty)
scriptSig: (empty)

Non-standard scripts

Anyone-can-spend:

scriptPubKey: (empty)
scriptSig: OP_TRUE