3
I've been looking at the version numbers of blocks, but I'm getting strange results from bitcoin-cli getblock.
"version": 536870913
However, when I run the same command with the false option (to get the serialized block data), it shows a version number of 1:
"result": "010000 ...
Why is this happening?
4
Great question. I had to do some research to find out.
Currently version is actually 4 bytes. In the case of this block (and many other recent blocks, as it turns out) it's 01000020. This is little endian, so when you reverse the bytes in hex it's:
0x20000001 = 536870913
Which in binary is:
00100000000000000000000000000001
It turns out that the bits here follow the BIP0009 spec. You can get a more user-friendly explanation of BIP0009 here. Essentially, BIP0009 specifies that version bits are to be used to signal support for a soft-fork. In this particular case by using that that extra "1" at the end, the miner that mined this block is expressing support for BIP0112 otherwise known as OP_CHECKSEQUENCEVERIFY.
