Taproot activation proposal 202102

Expected timeline:

• 2021 March 17-31: Full node software released with Taproot activation deployment.
• 2021 July 23: Economic majority has upgraded. Miner signalling begins to indicate preparedness to protect the economic minority who haven’t upgraded yet.
• 2 weeks after 90% of hashrate signals: Taproot activates. Economic majority enforces, while miners protect the economic minority until they upgrade as well.
• 2022 August 1: Entire economy has upgraded.

For explanations of the various parameters, see BIP 8.

• name=taproot
  • Rationale: Already used in Bitcoin Core (for Signet and tests), no reason to change (BIP8’s “bipN” recommendation not applicable due to 2 Taproot BIPs)

• bit=2
  • Rationale: Already used in Bitcoin Core (for tests), no reason to change
  • Note: Bit 2 is unaffected by ongoing miner ASICBoost false-bit-spam.

• startheight=693504 (~2021 July 23rd)
  • Rationale 1:
    • Earliest activation (MASF) takes 4 weeks, coinciding with Bitcoin Core 0.20 Maintenance End. Therefore, a backport of Taproot to 0.20 (complex and would need validation) can be avoided.
  • Rationale 2:
    • ~26 weeks (6.5 months) between meeting and earliest activation.
    • 1.5 months to prepare and release activation + 5 months for the economic majority to upgrade.

• timeoutheight=745920 (~2022 July 22nd / 1 year after signalling begins)
  • Rationale:
    • Plenty of time and community support.
    • Remaining economic minority can be expected to upgrade within a year.

• lockinontime= NO CONSENSUS WAS REACHED

• threshold=1815 (90%)
  • Rationale 1:
    • High enough to ensure the Taproot chain always has a lead ahead of any invalid chains.
  • Rationale 2:
    • Low enough to avoid a sudden malicious stall of activation by rented or unknown miners.
    • 90% of hashrate has already committed to work toward Taproot activation.