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Output (Transaction Output)

An introduction to the data structure and function of transaction outputs.

What is a Transaction Output?​

A Bitcoin transaction output (Transaction Output, abbreviated as "vout") refers to the payment destination and amount included in a Bitcoin transaction. Each output defines the recipient and the amount of Bitcoin they will receive.

Structure of Transaction Output Fields​

Each transaction output contains the following key fields:

1. Value​

This is an 8-byte integer representing the amount of Bitcoin in the output, measured in satoshis. One Bitcoin equals 100,000,000 satoshis.

2. ScriptPubKey​

The locking script is a variable-length field that defines how to unlock and use this output. It is usually the recipient's public key hash (P2PKH) or other complex scripts.

Example​

Here is an example of a Bitcoin transaction output, represented in JSON format:

"vout": [
  {
    "value": 0.01500000,
    "n": 0,
    "scriptPubKey": {
      "asm": "OP_DUP OP_HASH160 89abcdef... OP_EQUALVERIFY OP_CHECKSIG",
      "hex": "76a91489abcdef...",
      "reqSigs": 1,
      "type": "pubkeyhash",
      "addresses": [
        "1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa"
      ]
    }
  }
]

In this example:

  • value indicates the amount of Bitcoin the recipient will receive.
  • scriptPubKey contains details of the locking script.
  • n is the index position of the output.
  • reqSigs indicates the minimum number of signatures required to unlock this output.
  • type specifies the type of locking script (e.g., P2PKH).
  • addresses is the Bitcoin address of the recipient.

Functions of Transaction Outputs​

1. Specify Recipients​

Transaction outputs define the recipients of Bitcoin, ensuring that Bitcoin is correctly transferred to the intended destination addresses.

2. Locking and Unlocking Mechanism​

Through locking scripts, transaction outputs can set complex conditions to control the use of Bitcoin. Only by meeting these conditions can the Bitcoin be unlocked and used.

3. Multi-Signature Support​

Transaction outputs can support multi-signatures, specifying the number of signatures required to unlock Bitcoin through the reqSigs field, enhancing the security of transactions.

Types of Transaction Outputs​

1. Pay-to-PubKeyHash (P2PKH)​

The most common output type, where the locking script contains the recipient's public key hash. Unlocking requires providing the corresponding public key and signature.

2. Pay-to-Script-Hash (P2SH)​

The output is locked to a script corresponding to a hash value. Unlocking requires providing the script that generates this hash value along with the necessary inputs.

3. Multi-Signature Output​

Requires multiple signatures to unlock Bitcoin, typically used for transactions that need joint approval from multiple parties.

Summary​

Transaction outputs are a key component of Bitcoin transactions, defining the recipients and amounts of Bitcoin. Through locking scripts, transaction outputs ensure that Bitcoin can only be used by legitimate recipients. Understanding the structure and function of transaction outputs helps to gain a deeper understanding of the working principles and security mechanisms of Bitcoin transactions.