Inspired by the concept of code golf, this project aims to achieve the most compact encoding of Bitcoin's header chain.
If you have a full node running with the REST option enabled, you can get a copy of the header chain by running:
$ gradle run
Once you have a copy of the header chain, you can run:
$ gradle build
$ java -jar build/libs/headergolf-0.1.0.jar -i headers.dat -o compressed.dat
The previous block hash doesn't need to be stored as it can be computed from the previous header.
As the very first header's previous hash is zero-filled, we don't even need to store the first one:
prevHashN = sha256(sha256(headerN-1))
prevHash0 = 0x000000....0000000000000
Since version numbers are mostly 1 or 2, they can be efficiently compressed using FastFPOR.
(inspired by this email)
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Include the bits only on headers with a height that is a multiple of 2016 since it does not change in between.
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Compress time to two bytes by using the bounds on allowed values from the consensus rules.
These results were obtained for the header chain at block #539964. The raw file is 43,197,200 bytes.
| Algorithm | Compressed size | Compression ratio |
|---|---|---|
| GZIP | 36,978,199 bytes | 1.168 |
| LZMA | 35,619,153 bytes | 1.213 |
| 7z | 35,602,912 bytes | 1.213 |
| headergolf | 24,370,616 bytes | 1.772 |