bitcoin-bitcoin-core/test/functional/data

Various test vectors

mainnet_alt.json

For easier testing the difficulty is maximally increased in the first (and only) retarget period, by producing blocks approximately 2 minutes apart.

The alternate mainnet chain was generated as follows:

• use faketime to set node clock to 2 minutes after genesis block
• mine a block using a CPU miner such as https://github.com/pooler/cpuminer
• restart node with a faketime 2 minutes later

for i in {1..2015}
do
 faketime "`date -d @"$(( 1231006505 + $i * 120 ))"  +'%Y-%m-%d %H:%M:%S'`" \
 bitcoind -connect=0 -nocheckpoints -stopatheight=$i
done

The CPU miner is kept running as follows:

./minerd --coinbase-addr 1NQpH6Nf8QtR2HphLRcvuVqfhXBXsiWn8r --no-stratum --algo sha256d --no-longpoll --scantime 3 --retry-pause 1

The payout address is derived from first BIP32 test vector master key:

pkh(xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi/44h/0h/0h/<0;1>/*)#fkjtr0yn

It uses pkh() because tr() outputs at low heights are not spendable (unexpected-witness).

This makes each block determinisic except for its timestamp and nonce, which are stored in mainnet_alt.json and used to reconstruct the chain without having to redo the proof-of-work.

The timestamp was not kept constant because at difficulty 1 it's not sufficient to only grind the nonce. Grinding the extra_nonce or version field instead would have required additional (stratum) software. It would also make it more complicated to reconstruct the blocks in this test.