# Gavin Andresen
# 2011-11-23 01:25:43
# https://bitcointalk.org/index.php?topic=50223.msg627957#msg627957

In the spirit of "do the simplest possible thing that works..."  I think I see a very simple thing that will work. @p{par}

The simple additional rule for the testnet: @p{par}

If current_block_timestamp - previous_block_timestamp @s{gt} 20 minutes: @p{brk}
  block difficulty = minimum difficulty @p{par}

And that's it. @p{par}

If mining is proceeding normally and most blocks are produced in less than 20 minutes, then the rules are exactly the same as the main network. @p{par}

But if somebody has driven difficulty way up, then the new rule acts as a safety valve, ensuring that new blocks are created at least once every 20-something minutes or so.  After a month of "safety valve blocks" the difficulty would be calculated as normal, and would get cut in (approximately) half. @p{par}

This does make the testnet block chain more susceptible to forks @p{--} somebody with a bunch of hashing power can pretty easily invalidate a long chain of 20-minute, min-difficulty blocks if they want to. And there is likely to be a flurry min-difficulty blocks produced/announced every 20 minutes. But that could be considered a feature (test your block-chain-reorganization code!). @p{brk}