Why is *double* SHA-256 hashing used in the block header?Both the previous block's header hash and Merkle root hash use double SHA-256 hashing.
Why are two rounds used?
Source: Why is *double* SHA-256 hashing used in the block header? (https://bitcoin.stackexchange.com/questions/112854/why-is-double-sha-256-hashing-used-in-the-block-header)