Bitcoin: Valid bits of block header versions

Supporting Bit Version Headers in Bitcoin

Bitcoin’s block header structure has been the subject of much curiosity and confusion among developers, traders, and enthusiasts alike. One aspect of this structure that can be puzzling is the changing bit version number, which seems to be updated randomly at each mining operation. In this article, we’ll delve into the details behind block header versions in Bitcoin and explore what values ​​miners can adjust.

The Block Header Structure

A Bitcoin block consists of several components, including:

• Version: The first field, representing the version number of the block header.

• Inflation Adjustment Factor (AF): A field that adjusts the inflation rate based on a given timestamp and maximum inflation.

• Merkle Root: A hash of the Merkle tree containing all transactions in the block.

• Transaction Count**: The total number of transactions included in the block.

Bit Version Numbers

The first two fields,VersionandInflation Adjustment Factor (AF), have fixed values:

• Version: 0x00000001 (always 1)

• Inflation Adjustment Factor (AF): never changes (it's a constant)

However, the third field,Merkle Root, has two possible versions:0x00000000and0xFFFFFFFF. The block header can be divided into two parts:

• Header Block: contains only the first 32 bytes of the header.

• Data Block: contains all data stored in the block (transactions, Merkle root, etc.).

Miner-Adjusted Bit Version Numbers

When miners update their block headers at each mining operation, they can adjust two values:

• Versionbit: this value is not affected by miner adjustments and remains 1.

• Inflation Adjustment Factor (AF): as mentioned earlier, the value does not change.

The third field,Merkle Root, has a random version number that miners can manipulate:

• 0x00000000

• 0xFFFFFFFF

Miners can choose to update either or both of these values ​​with new data. However, there are some caveats:

• TheInflation Adjustment Factor (AF)value remains the same throughout the block's lifetime.

• TheMerkle Rootversion number must be a valid Merkle root for the transactions in the block.

Why Random Version Numbers?

The use of random versions forMerkle RootandVersionis likely due to historical reasons:

• In older versions of Bitcoin (pre-2010s), miners could only update their block headers with data from previous blocks. With more efficient mining algorithms, it became possible to mine new blocks without using prior block data.

• The random version numbers are used to prevent miners from exploiting weaknesses in the system by manipulating theInflation Adjustment Factor (AF)value.

Conclusion

In conclusion, Bitcoin's block header structure has a fixed first two fields but can have variable versions of three other fields:Merkle RootandVersion. Miners can adjust the values ​​ofInflation Adjustment Factor (AF)andMerkle Root`, but not the fixed values. Understanding these changes is crucial for developers, traders, and enthusiasts who rely on accurate block header information.

I hope this article has helped clarify the mysteries surrounding Bitcoin’s block headers!