The Bitcoin File Format

2- There is no doubt as to what the Bitcoin File Format is. It is described in Schedule 2 to the Particulars of Claim. The overall structure of a block comprises three parts:
1) a block header of 80 bytes; (2) the vtx number, of 1-9 bytes, which records the number of transactions in a variable VarInt; and
(3) the transactions recorded in the block, of variable size.

3 - The block header is always 80 bytes but Schedule 2 explains that it comprises various data fields as follows:

i) nVersion, 4 bytes in length comprising a 32 bit unsigned integer stored in little endian and representing the version of the block format;

ii) hashPrevBlock, 32 bytes in length, being a double hash of the previous block header stored in little endian – essentially the link to the previous block in the chain;

iii) hashMerkleRoot, again 32 bytes in length, comprising a double hash of the root of the Merkle tree of transactions stored in little endian;

iv) nTime, a 4 byte field, representing the time in seconds since 1 Jan 1970, in a 32 but unsigned integer in little endian;

v) nBits, a 4 byte field recording a measure of the difficulty target in compact format;

vi) nNonce, a 4 byte field. Nonce is a portmanteau of 'number used only once'. The Nonce is used in the proof of work algorithm and is effectively the number that blockchain miners are solving for.

4 - Schedule 2 goes on to describe the Transactions part of the block. There are two types: normal and 'coinbase' transactions. Further paragraphs in Schedule 2 explain the general structure of a transaction, the structure of an input and an output in a normal transaction (which differ) and the structure of the input in a coinbase transaction (the output having the same structure), in a similar manner to the explanation of the additional structure in the header, which I summarised above. It is not necessary for me to set out these structures.

Copyright

IN THE HIGH COURT OF JUSTICE BUSINESS AND PROPERTY COURTS OF ENGLAND AND WALES INTELLECTUAL PROPERTY LIST (ChD)

Rolls Building, Fetter Lane
London, EC4A 1NL
7th February 2023

https://www.bailii.org/ew/cases/EWHC/Ch/2023/222.html