On May 22, 2017 23:05, "Peter Todd" wrote: On Mon, May 22, 2017 at 03:05:49AM -0400, Russell O'Connor via bitcoin-dev wrote: > MerkleRoot := SHA256(SHA256(LeftRoot ⋅ RightRoot)) > sha256Compress : Word256 × Word512 -> Word256 To be clear, what math operations do you mean by "⋅" and "×"? By "⋅", I usually mean concatenation (though I also use it for function composition in one instance). By "×", I mean the Cartesian product.