Timewarp attack 600 second grace period

Protocol Design
37

I’m still trying to understand whether the difficulty decrease compounds. Take the following (same MTP simplification as above):

  • Period 0: [0, 0, 0, …, 0, 0, P].
  • Period 1: [P-G, P-G, …, P-G, 2P].
  • Period 2: [2P-G, …, 3P].
  • Period 3: [3P-G, …, 4P],
  • …
  • Period k: [kP-G, …, (1+k)P].

So each period is stretched by G, causing the difficulty to drop every time. For G = 2 hours, this would be 0.6% per retarget period. That translates to about 15% per year.

Note that any difficulty decrease accumulation can be reset by an honest miner finding the last block of any retarget period.

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