Did Merkle invent cryptographic hashing?
I think the first paragraph of this document show be helpful.

The Rabin reference at the bottom of the text is from 1978, and the impression I get from p3 of this document is that he came up with a linear iterated hash function in that 1978 paper. So maybe Rabin invented it. 

I think we can be pretty sure it was either Merkle, Rabin or Yuval (if you must choose one), but that sounds like an answer correct for a good deal of history questions in this field. 

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