Can a data be altered in a blockchain without changing its hash

Question

I wish to  build something like proof of authenticity on blockchain.

I thought of using this approach:  storing the hash of data in ethereum blockchain and the data itself in some storage elsewhere.

Let's say it's an article we are talking about. If one needs proof that this article existed at some point of time, he can use the hash algorithm to generate hash from the article stored in whatever database/datastorage and compare it with the hash stored in blockchain.

can someone tell me if this would work. Also, is there a way to change the data data without changing its hash

Answer 1

Yes, it should work. The authentication practice you are trying to build is very musch possible with hash functions. Ensuring that you are using one way hashing functions(example SHA256) which has strong cryptographic properties(strong collision resistance), it is nearly impossible to have data streams with same hash.