Bitcoin Attacks that are Probably not a problem - Discussion

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I am wondering that since the SHA256 hash function is often doubled hashed in Bitcoin (e.g. address creation, Merkle Tree of transactions) does this not mean that in the event that SHA256 is broken then there is adequate time to upgrade to a new more secure hash function?

Nothing to add other than this course is very useful!

Hi, an hash function is not same as encryption one.
Search the web to learn more about this difference, example at

A broken hash function would only mean it’s hash result could give a same output but for 2 different inputs, double hashing would mean the same for the broken prove, because in the event that there is a not equal to b and if A=hash( a ) and B = hash ( b ) and if A=B then hash(hash(a)) = hash(hash(b))

So I would left here your question in other words would perhaps be: Why Bitcoin uses double hashes sometimes in its operation?