Bitcoin raw transaction and transaction id

Bitcoin Raw Transaction

• A raw transaction is a way to construct a transaction by specifying the UTXO (which bitcoins to spend) and where to send them.
• This raw transaction can be signed with your private key, and the signed transaction can be broadcasted to the Bitcoin network.
• It is intended for developers or very sophisticated end-users for low-level access to transaction creation and broadcast.

Big Endian Little Endian

• Big Endian - Machine stores the most significant bytes first.

•  Little Endian - Machine stores the least significant bytes first.

Satoshi

• A Satoshi is the smallest unit of Bitcoin.
• 1$ = 100 cent
• 1 cent = 0.01 $
• 1 BTC = 100,000,000 satoshi (108)
• 1 satoshi = 0.000000001 BTC

• A transaction id (TXID) or transaction hash is a long string of numbers:
• A transaction if can be used to look up a transaction on the blockchain.
• Transaction ids are also used to create a Merkle Tree (more about this in a later video)
• A Bitcoin transaction id is always 32 bytes (64 characters) and contains hexadecimal values.

Bitcoin Transaction ID

To calculate the transaction id of a transaction:

• Create the raw transaction: raw _tx
• Convert raw_tx hex string into the corresponding unicode: data = raw_tx.decode("hex")
• Apply the sha256 hash function twice: hash = sha256(sha256(data))
• Take the little endian order of the hash: hash_little_ehdian = little_endian(hash)