// Written in 2014 by Andrew Poelstra <apoelstra@wpsoftware.net>
// SPDX-License-Identifier: CC0-1.0
//! Bitcoin consensus parameters.
//!
//! This module provides a predefined set of parameters for different Bitcoin
//! chains (such as mainnet, testnet).
//!
use crate::network::constants::Network;
use crate::util::uint::Uint256;
/// Lowest possible difficulty for Mainnet. See comment on Params::pow_limit for more info.
const MAX_BITS_BITCOIN: Uint256 = Uint256([
0x0000000000000000u64,
0x0000000000000000u64,
0x0000000000000000u64,
0x00000000ffff0000u64,
]);
/// Lowest possible difficulty for Testnet. See comment on Params::pow_limit for more info.
const MAX_BITS_TESTNET: Uint256 = Uint256([
0x0000000000000000u64,
0x0000000000000000u64,
0x0000000000000000u64,
0x00000000ffff0000u64,
]);
/// Lowest possible difficulty for Regtest. See comment on Params::pow_limit for more info.
const MAX_BITS_REGTEST: Uint256 = Uint256([
0x0000000000000000u64,
0x0000000000000000u64,
0x0000000000000000u64,
0x7fffff0000000000u64,
]);
/// Parameters that influence chain consensus.
#[derive(Debug, Clone)]
pub struct Params {
/// Network for which parameters are valid.
pub network: Network,
/// Block height at which BIP16 becomes active.
pub bip16_height: u32,
/// Block height at which BIP34 becomes active.
pub bip34_height: u32,
/// Block height at which BIP65 becomes active.
pub bip65_height: u32,
/// Block height at which BIP66 becomes active.
pub bip66_height: u32,
/// Minimum blocks including miner confirmation of the total of 2016 blocks in a retargeting period,
/// (nPowTargetTimespan / nPowTargetSpacing) which is also used for BIP9 deployments.
/// Examples: 1916 for 95%, 1512 for testchains.
pub rule_change_activation_threshold: u32,
/// Number of blocks with the same set of rules.
pub miner_confirmation_window: u32,
/// Proof of work limit value. It contains the lowest possible difficulty.
///
/// Note that this value differs from Bitcoin Core's powLimit field in that this value is
/// attainable, but Bitcoin Core's is not. Specifically, because targets in Bitcoin are always
/// rounded to the nearest float expressible in "compact form", not all targets are attainable.
/// Still, this should not affect consensus as the only place where the non-compact form of
/// this is used in Bitcoin Core's consensus algorithm is in comparison and there are no
/// compact-expressible values between Bitcoin Core's and the limit expressed here.
pub pow_limit: Uint256,
/// Expected amount of time to mine one block.
pub pow_target_spacing: u64,
/// Difficulty recalculation interval.
pub pow_target_timespan: u64,
/// Determines whether minimal difficulty may be used for blocks or not.
pub allow_min_difficulty_blocks: bool,
/// Determines whether retargeting is disabled for this network or not.
pub no_pow_retargeting: bool,
}
impl Params {
/// Creates parameters set for the given network.
pub fn new(network: Network) -> Self {
match network {
Network::Bitcoin => Params {
network: Network::Bitcoin,
bip16_height: 173805,
bip34_height: 227931, // 000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8
bip65_height: 388381, // 000000000000000004c2b624ed5d7756c508d90fd0da2c7c679febfa6c4735f0
bip66_height: 363725, // 00000000000000000379eaa19dce8c9b722d46ae6a57c2f1a988119488b50931
rule_change_activation_threshold: 1916, // 95%
miner_confirmation_window: 2016,
pow_limit: MAX_BITS_BITCOIN,
pow_target_spacing: 10 * 60, // 10 minutes.
pow_target_timespan: 14 * 24 * 60 * 60, // 2 weeks.
allow_min_difficulty_blocks: false,
no_pow_retargeting: false,
},
Network::Testnet => Params {
network: Network::Testnet,
bip16_height: 514,
bip34_height: 21111, // 0000000023b3a96d3484e5abb3755c413e7d41500f8e2a5c3f0dd01299cd8ef8
bip65_height: 581885, // 00000000007f6655f22f98e72ed80d8b06dc761d5da09df0fa1dc4be4f861eb6
bip66_height: 330776, // 000000002104c8c45e99a8853285a3b592602a3ccde2b832481da85e9e4ba182
rule_change_activation_threshold: 1512, // 75%
miner_confirmation_window: 2016,
pow_limit: MAX_BITS_TESTNET,
pow_target_spacing: 10 * 60, // 10 minutes.
pow_target_timespan: 14 * 24 * 60 * 60, // 2 weeks.
allow_min_difficulty_blocks: true,
no_pow_retargeting: false,
},
Network::Regtest => Params {
network: Network::Regtest,
bip16_height: 0,
bip34_height: 100000000, // not activated on regtest
bip65_height: 1351,
bip66_height: 1251, // used only in rpc tests
rule_change_activation_threshold: 108, // 75%
miner_confirmation_window: 144,
pow_limit: MAX_BITS_REGTEST,
pow_target_spacing: 10 * 60, // 10 minutes.
pow_target_timespan: 14 * 24 * 60 * 60, // 2 weeks.
allow_min_difficulty_blocks: true,
no_pow_retargeting: true,
},
Network::Testnet4 => Params {
network: Network::Testnet4,
bip16_height: 1,
bip34_height: 2,
bip65_height: 3,
bip66_height: 4,
rule_change_activation_threshold: 1512, // 75%
miner_confirmation_window: 2016,
pow_limit: MAX_BITS_TESTNET,
pow_target_spacing: 10 * 60, // 10 minutes.
pow_target_timespan: 14 * 24 * 60 * 60, // 2 weeks.
allow_min_difficulty_blocks: true,
no_pow_retargeting: false,
},
Network::Scalenet => Params {
network: Network::Scalenet,
bip16_height: 1,
bip34_height: 2,
bip65_height: 3,
bip66_height: 4,
rule_change_activation_threshold: 1512, // 75%
miner_confirmation_window: 2016,
pow_limit: MAX_BITS_TESTNET,
pow_target_spacing: 10 * 60, // 10 minutes.
pow_target_timespan: 14 * 24 * 60 * 60, // 2 weeks.
allow_min_difficulty_blocks: true,
no_pow_retargeting: false,
},
Network::Chipnet => Params {
network: Network::Chipnet,
bip16_height: 1,
bip34_height: 2,
bip65_height: 3,
bip66_height: 4,
rule_change_activation_threshold: 1512, // 75%
miner_confirmation_window: 2016,
pow_limit: MAX_BITS_TESTNET,
pow_target_spacing: 10 * 60, // 10 minutes.
pow_target_timespan: 14 * 24 * 60 * 60, // 2 weeks.
allow_min_difficulty_blocks: true,
no_pow_retargeting: false,
},
}
}
/// Calculates the number of blocks between difficulty adjustments.
pub fn difficulty_adjustment_interval(&self) -> u64 {
self.pow_target_timespan / self.pow_target_spacing
}
}