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Author: KaKeimei

docs/blockchain/bitcoin-basics/block/bits.md

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+
 # Bits
+
+Introducing the difficulty bits representing the difficulty target of a block.
+
+## What are Difficulty Bits (Bits)?
+
+Difficulty bits (Bits) are a field in the Bitcoin block header that represent the current mining difficulty. It is a
+compact form of the target threshold, and miners must generate a block hash that is less than this target value for it
+to be accepted by the network. The difficulty bits are encoded in a compact way to reduce data storage and transmission
+overhead.
+
+## The Role of Difficulty Bits
+
+### 1. Controlling Block Generation Time
+
+Difficulty bits directly affect the mining difficulty, thereby controlling the block generation time. The goal of the
+Bitcoin network is to generate a new block every 10 minutes. By adjusting the difficulty bits, the network ensures that
+block generation time stays within the target range despite changes in miner hash power.
+
+### 2. Ensuring Network Security
+
+By adjusting mining difficulty, the Bitcoin network can prevent malicious actors from easily generating new blocks. As
+miner hash power increases, the network automatically raises the mining difficulty, increasing the cost and difficulty
+of attacks, thereby ensuring the security and stability of the network.
+
+## Calculating Difficulty Bits
+
+The calculation process of difficulty bits is as follows:
+
+1. **Target Threshold**: Represent the target threshold as a 256-bit large integer.
+2. **Compact Representation**: Convert the target threshold into a compact form, represented as the difficulty bits
+   field.
+
+### Example
+
+Assuming the target threshold is `0x1d00ffff`, the corresponding difficulty bits representation is:
+
+```
+0x1d00ffff = 0x00ffff * 2^(8*(0x1d - 3))
+```
+
+## Difficulty Adjustment Mechanism
+
+The Bitcoin network adjusts the difficulty every 2016 blocks (approximately every two weeks). Based on the actual
+generation time of the past 2016 blocks, the network adjusts the difficulty bits so that the next 2016 blocks'
+generation time approaches the target time (two weeks).
+
+### Adjustment Formula
+
+New Difficulty = Old Difficulty * (Actual Generation Time / Target Generation Time)
+
+## Obtaining Difficulty Bits Information
+
+Using the Bitcoin Core client, you can obtain the difficulty bits information of the current block through the command
+line interface (CLI):
+
+### Obtaining Latest Block Information
+
+```bash
+mvc-cli getblockchaininfo
+```
+
+### Obtaining Specific Block Information
+
+First, get the block hash:
+
+```bash
+mvc-cli getblockhash <height>
+```
+
+Then, use the block hash to get detailed block information, including the difficulty bits field:
+
+```bash
+mvc-cli getblock <blockhash>
+```
+
+## Summary
+
+Difficulty bits (Bits) are an important field in the Bitcoin blockchain, representing mining difficulty, controlling
+block generation time, and ensuring network security. Understanding the principles and calculation methods of difficulty
+bits helps to gain a deeper understanding of the Bitcoin network's operation mechanism and its application in
+decentralized systems.

docs/blockchain/bitcoin-basics/block/blk-dat.md

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+
 # blk.dat
+
+Introducing the storage format of Bitcoin block files blk.dat.
+
+## What is blk.dat File
+
+Bitcoin nodes use blk.dat files to store blockchain data. Each blk.dat file contains a series of Bitcoin blocks stored
+in a compact binary format. These files are located in the Bitcoin data directory, usually under the `blocks/`
+subdirectory.
+
+## Structure of blk.dat File
+
+### Block File Header
+
+Each blk.dat file begins with a 4-byte magic number, which is used to mark the start of a block. In Bitcoin, the magic
+number is `0xD9B4BEF9`.
+
+### Block Data
+
+Following the magic number is the block data. The block data includes:
+
+1. **Block Size**: A 4-byte integer representing the size of the block (in bytes).
+2. **Block Content**: The actual block data, including the block header and block body (transaction data).
+
+The order of the block data is: magic number -> block size -> block content. Multiple blocks are stored consecutively in
+a single blk.dat file.
+
+### File Rotation
+
+When a blk.dat file reaches its maximum size (default is 2GB), the Bitcoin node creates a new blk.dat file, with the
+filenames incrementing sequentially, such as `blk00000.dat`, `blk00001.dat`, and so on.
+
+## How to Read blk.dat File
+
+Reading a blk.dat file can be done using the Bitcoin Core client or custom parsing tools. The parsing process involves
+the following steps:
+
+1. **Open File**: Open the blk.dat file in binary mode.
+2. **Read Magic Number**: Verify if it is a valid block start.
+3. **Read Block Size**: Get the block size information.
+4. **Read Block Content**: Read the complete block data based on the block size.
+5. **Repeat Steps**: Continue reading the next block until the end of the file.
+
+### Example Code
+
+Here is a simple Python example code to parse a blk.dat file:
+
+```python
+import struct
+
+def read_block(file):
+    magic = file.read(4)
+    if not magic:
+        return None
+    size = struct.unpack("<I", file.read(4))[0]
+    block_data = file.read(size)
+    return block_data
+
+with open('blk00000.dat', 'rb') as f:
+    while True:
+        block = read_block(f)
+        if block is None:
+            break
+        print(f"Read block of size: {len(block)}")
+```
+
+## Importance of blk.dat Files
+
+1. **Blockchain Storage**: blk.dat files are the foundation for Bitcoin nodes to store the complete blockchain data,
+   ensuring all transactions and block records are fully preserved.
+2. **Node Synchronization**: When new nodes join the network, they can quickly synchronize blockchain data by
+   downloading and parsing blk.dat files.
+3. **Data Recovery**: In case of data corruption or node restart, blk.dat files provide a reliable way to recover
+   blockchain data.
+
+## Summary
+
+blk.dat files are crucial components for storing blockchain data in Bitcoin nodes. By storing block data in a compact
+binary format, they ensure the integrity and reliability of the blockchain. Understanding the structure and reading
+methods of blk.dat files helps to deeply grasp the operation mechanism of Bitcoin nodes and blockchain data management.

docs/blockchain/bitcoin-basics/block/block-hash.md

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+
 # Block Hash
+
+Introducing how the block ID is calculated.
+
+## What is a Block Hash
+
+A block hash is a unique identifier in the blockchain, generated by performing a double SHA-256 hash on the block
+header. The block hash is used to identify and reference specific blocks, ensuring the security and integrity of the
+blockchain.
+
+## Block Hash Generation Process
+
+### 1. Constructing the Block Header
+
+The block header contains the following fields:
+
+- Version ([Version](version.md))
+- Previous Block Hash ([Previous Block Hash](previous-block.md))
+- Merkle Root ([Merkle Root](merkle-root.md))
+- Timestamp ([Timestamp](time.md))
+- Difficulty Target ([Bits](bits.md))
+- Nonce ([Nonce](nonce.md))
+
+### 2. Hashing Process
+
+1. Convert the block header's content into a byte sequence.
+2. Perform the first SHA-256 hash on the byte sequence to get Hash 1.
+3. Perform the second SHA-256 hash on Hash 1 to get the final block hash.
+
+### Example Code
+
+Here is an example code to generate a block hash:
+
+```ruby
+require 'digest'
+
+# Block header fields
+version = "01000000"
+previousblock = "0000000000000000000000000000000000000000000000000000000000000000"
+merkleroot = "3ba3edfd7a7b12b27ac72c3e67768f617fc81bc3888a51323a9fb8aa4b1e5e4a"
+time = "29ab5f49"
+bits = "ffff001d"
+nonce = "1dac2b7c"
+
+blockheader = version + previousblock + merkleroot + time + bits + nonce
+
+# Convert to byte sequence
+bytes = [blockheader].pack("H*")
+
+# First SHA-256 hash
+hash1 = Digest::SHA256.digest(bytes)
+
+# Second SHA-256 hash
+hash2 = Digest::SHA256.digest(hash1)
+
+# Convert result to hexadecimal string
+blockhash = hash2.unpack("H*")[0]
+
+puts blockhash
+```
+
+## Functions of a Block Hash
+
+1. **Block Identification**: The block hash serves as the unique identifier for a block, used to quickly locate and
+   reference specific blocks in the blockchain.
+2. **Ensuring Integrity**: By hashing the block header, the block hash ensures the integrity and immutability of the
+   block data.
+3. **Consensus Mechanism**: Miners must find a nonce that makes the block hash less than the target value when
+   generating new blocks, ensuring the proof-of-work mechanism of the blockchain.
+
+## Summary
+
+The block hash is generated by performing a double SHA-256 hash on the block header and is a key element in identifying
+and verifying blocks in the blockchain. Understanding the block hash generation process and its functions helps to grasp
+the security and operation mechanisms of the blockchain.

docs/blockchain/bitcoin-basics/block/merkle-root.md

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+
 # Merkle Root
+
+Introducing the concept of the Merkle root.
+
+## What is a Merkle Root
+
+The Merkle root is a key component in the blockchain, used to verify the integrity and consistency of all transactions
+within a block. It is a single hash value obtained by recursively hashing all transaction hashes (TXIDs) in the block.
+The Merkle root is included in the block header to ensure the immutability of the transaction data within the block.
+
+## Generation of the Merkle Root
+
+The process of generating the Merkle root is as follows:
+
+1. **Hash Transactions**: Hash all transaction hashes (TXIDs) within the block.
+2. **Pairwise Hashing**: Combine the hashed transactions in pairs and hash them again. If the number of transactions is
+   odd, the last transaction hash is paired with itself and hashed.
+3. **Recursive Hashing**: Repeat the above steps until only one hash value remains, which is the Merkle root.
+
+### Example
+
+Suppose there are four transaction TXIDs: A, B, C, D.
+
+1. **Initial Hashing**:
+    - Hash A, B, C, D to get Ha, Hb, Hc, Hd.
+2. **Pairwise Hashing**:
+    - Combine Ha with Hb, and Hc with Hd, to get Ha+b, Hc+d.
+3. **Final Hashing**:
+    - Combine Ha+b with Hc+d to get the Merkle root Hroot.
+
+## Functions of the Merkle Root
+
+### 1. Verifying Transaction Integrity
+
+The Merkle root provides an efficient way to verify the integrity of all transactions within a block. By checking the
+Merkle root, it can be determined whether the transactions in the block have been tampered with.
+
+### 2. Improving Data Processing Efficiency
+
+The Merkle root allows lightweight nodes (SPV nodes) to verify the presence of specific transactions in a block by
+downloading only the block header rather than the entire block, thereby improving data processing efficiency and
+bandwidth utilization.
+
+### 3. Ensuring Data Security
+
+Through the Merkle root, the integrity of blockchain data can be verified, preventing malicious nodes from tampering
+with transaction records and ensuring the security and reliability of the blockchain.
+
+## Merkle Tree and Lightweight Wallets
+
+The Merkle tree structure not only enhances blockchain security but also supports the implementation of lightweight
+wallets. Lightweight wallets do not need to download the entire blockchain; they only need to download the block headers
+and corresponding Merkle proofs to verify the existence and validity of transactions. This significantly reduces the
+need for storage and computational resources, making blockchain technology more accessible.
+
+## Summary
+
+The Merkle root is an important component of blockchain technology, generated through recursive hashing to verify the
+integrity and consistency of transactions within a block. It not only enhances blockchain security but also supports the
+efficient implementation of lightweight wallets, optimizing data processing and verification efficiency. Understanding
+how the Merkle root works helps to deeply grasp blockchain technology and its application in decentralized systems.

docs/blockchain/bitcoin-basics/block/nonce.md

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+
 # Nonce
+
+Introducing the nonce field in the block header.
+
+## What is a Nonce
+
+Nonce is a 32-bit field in the block header, representing a random number used only once. In the Bitcoin mining process,
+miners continuously change the nonce value and calculate the hash of the block header until they find a hash that meets
+specific conditions (i.e., less than the current network difficulty target).
+
+## Position of Nonce in the Block Header
+
+The block header contains the following fields:
+
+- Version
+- Previous Block Hash
+- Merkle Root
+- Timestamp
+- Bits (Difficulty Target)
+- Nonce
+
+## Function of Nonce
+
+### 1. Mining Process
+
+In the Bitcoin mining process, miners continuously try different nonce values to find a valid block where the hash of
+the block header is less than the current difficulty target. When such a nonce is found, the block is considered valid
+and can be added to the blockchain.
+
+### 2. Ensuring Fair Competition
+
+By using the nonce, miners can compete fairly, ensuring that block generation is random and not monopolized by a
+specific miner.
+
+### 3. Preventing Reuse
+
+The uniqueness and randomness of the nonce ensure the uniqueness of each block, preventing block reuse and duplicate
+transaction confirmations.
+
+## Nonce Calculation
+
+When miners generate a new block, they continuously change the nonce value and perform a double SHA-256 hash on the
+block header until they find a hash that meets the required conditions.
+
+### Example
+
+Here is a simple pseudo-code example demonstrating how to mine by changing the nonce value:
+
+```python
+import hashlib
+
+def mine_block(block_header, difficulty_target):
+    nonce = 0
+    while True:
+        block_header_with_nonce = block_header + str(nonce)
+        hash_result = hashlib.sha256(hashlib.sha256(block_header_with_nonce.encode()).digest()).hexdigest()
+        if int(hash_result, 16) < difficulty_target:
+            return nonce, hash_result
+        nonce += 1
+
+block_header = "example_block_header"
+difficulty_target = 0x00000fffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+
+nonce, valid_hash = mine_block(block_header, difficulty_target)
+print(f"Valid Nonce: {nonce}, Valid Hash: {valid_hash}")
+```
+
+## Summary
+
+Nonce is a crucial field in the Bitcoin block header. By continuously changing the nonce value and performing hash
+calculations, miners can find a valid block that meets the specific difficulty target, ensuring the security and
+fairness of the blockchain. Understanding the function and calculation process of the nonce helps to deeply understand
+the Bitcoin mining mechanism and its application in decentralized systems.