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I under that merkle tree use double hashing (HA = SHA256(SHA256(Transaction A)). Curious for answers to the following:

  1. Why is there a need to hash it twice?
  2. What is the difference between hashing it twice this way or using the hashing method for keys (RIPEMD(SHA256(P))
  3. Is there any value in hashing more than 2 times?