# BSV Transactions and SHA-256

#### What is a Transaction?

The **BSV blockchain** is an **electronic cash system** built on:

* **2.1 quadrillion indivisible units** called **satoshis**.
* A **shared public ledger** that records every transfer of ownership.

1 BSV = **100,000,000 satoshis**.\
Satoshis are the **smallest unit of account** in BSV. Ownership of any amount is transferred through a **transaction** — a record added to the ledger.

***

#### What a Transaction Contains

Each transaction specifies:

* **The amount** of satoshis being transferred.
* **The source** of these satoshis (**input UTXOs**).
* **The destination** of these satoshis (**output UTXOs**).
* Transactions **consume input UTXOs** and **create new output UTXOs**.
* Every UTXO has a **locking script** (lockScript or scriptSig) written in **Bitcoin Script** — a minimal, stack-based language.
* To spend a UTXO, the sender must provide an **unlocking script** (unlockScript or scriptPubKey) that satisfies the locking conditions.

👉 **Predicate system:** A script resolves to either **true** or **false**. If true, ownership of satoshis is transferred.

<br>

<figure><img src="/files/dLJ973TpKYqLXlFes20b" alt=""><figcaption></figcaption></figure>

#### Transactions and Digital Signatures

Every satoshi is part of a **chain of digital signatures** tracing back to Bitcoin’s **Genesis block (2009)**.

* Each transaction adds a new link in this chain.
* This ensures **ownership history** is preserved.

***

#### SHA-256 and Transaction IDs

Once a transaction is constructed and serialized into **raw hexadecimal (HEX)**, it is hashed using **double SHA-256**.

* The result is a **Transaction ID (TXID)**.
* TXIDs allow nodes to:
  * Organize transactions in **memory pools**.
  * Place transactions into **Merkle Trees** for efficient validation.

👉 **Key takeaway:** SHA-256 hashing ensures each transaction has a **unique, tamper-proof identifier**.

***

#### Example: P2PKH Transaction

**Raw HEX form:**

```
010000000167e7105b52e8534596af29dba949921cffe3dbaa555b8ed96121346c6755adae000000006a47304402206e4db9dee8449b861e5fdc00ba3bdb80fba8cd52c75489376c54bd65d26262650220453569438e6bc6f957b1f7ff6fff4af2e42edaae1ac885382373d42fa569b17c41210267d2d1f8b3affffa10b68b2756ba7f6f4efafcadbecd145181016178d00b379bffffffff019c276bee000000001976a914accd105073775756cc04962bc1e4893694f50c5588ac00000000
```

\
Below, is the same transaction decoded and presented in a JSON format:

```
{ 
    "version": 1, 
    "size": 191, 
    "locktime": 0, 
    "vin": [ 
        { 
            "txid": "aead55676c342161d98e5b55aadbe3ff1c9249a9db29af964553e8525b10e767", 
            "vout": 0, 
            "scriptSig": { 
                "asm": "304402206e4db9dee8449b861e5fdc00ba3bdb80fba8cd52c75489376c54bd65d26262650220453569438e6bc6f957b1f7ff6fff4af2e42edaae1ac885382373d42fa569b17c[ALL|FORKID] 0267d2d1f8b3affffa10b68b2756ba7f6f4efafcadbecd145181016178d00b379b", 
                "hex": "47304402206e4db9dee8449b861e5fdc00ba3bdb80fba8cd52c75489376c54bd65d26262650220453569438e6bc6f957b1f7ff6fff4af2e42edaae1ac885382373d42fa569b17c41210267d2d1f8b3affffa10b68b2756ba7f6f4efafcadbecd145181016178d00b379b" 
            }, 
            "sequence": 4294967295 
        } 
    ], 
    "vout": [ 
        { 
            "value": 39.999999, 
            "n": 0, 
            "scriptPubKey": { 
                "asm": "OP_DUP OP_HASH160 accd105073775756cc04962bc1e4893694f50c55 OP_EQUALVERIFY OP_CHECKSIG", 
                "hex": "76a914accd105073775756cc04962bc1e4893694f50c5588ac", 
                "reqSigs": 1, 
                "type": "pubkeyhash", 
                "addresses": [ 
                    "mwGeB8HZwx22snzWoXRRfL2dhmJ4QXZr9V" 
                ] 
            } 
        } 
    ], 
    "time": 1645757424, 
} 
```

#### Transactions consist of 6 serialised elements:

#### Transaction Structure

* **Transactions** consist of **6 serialized elements**.
* **Input UTXOs** consist of **5 serialized elements**.
* **Output UTXOs** consist of **3 serialized elements**.

👉 Each part plays a role in **locking, unlocking, and transferring satoshis** across the blockchain.

&#x20;

<figure><img src="/files/Wk1khFTlWkjwJDn6Nuz1" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/py7f4njsUKPgN8SRG7U4" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/un3jByhK2sV7vIRmnoXg" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/T68VWXK3jg4HdkLXE6c2" alt=""><figcaption></figcaption></figure>

#### Input UTXOs consist of 5 serialised elements:

The below breaks-down the input UTXO from the above example transaction.

![](/files/Lu5Fh6ehBlCdJ7qG5pON)

#### Output UTXOs consist of 3 serialized elements:

The below table breaks-down the new output UTXO(s) from the above example transaction.

<figure><img src="/files/uIv5XIEOVYgRmK2wp67p" alt=""><figcaption></figcaption></figure>

✅ **Summary:** In BSV, transactions define **ownership transfers** of satoshis using **locking and unlocking scripts**. Each transaction is given a unique **TXID** by applying **double SHA-256**, making the system secure, verifiable, and scalable.


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