Is the only way to store some data (some hash value) in the blockchain is with contract store?

Question

I have a hash value and I need to store it in the blockchain as part of a transaction. and I need to look for that transaction with that hash later in time.

So creating a contract and storing it in its array/mapping. is this the only solution in Ethereum?

Answer 1

If you want an easy way to fetch that hash later on, you can:

• use the contract store: array or mapping
• or use the contract logging system with an event. event LogMyHash(bytes32 indexed theHash);. indexed will ensure you can query by the hash, like a mapping would do.

On the other hand if you did not care about retrieval, but all you wanted to do was quickly add your hash to a dummy transaction, you can send one to your other address and do eth.sendTransaction({ from: you, to: otherYou, data: theHash }). Since there is no code at your other address, data will not trigger anything. But the hash is there for anyone who knows where to look.