Can we store encrypted data into transaction

Question

Can Ethereum store an encrypted string, for instance, "hello world" into the storage in a simple storage smart contract?

And can Ethereum decipher this string "hello world" for specific list of allowed addresses?

Answer 1

Ethereum can store whatever bytes you want, so you can certainly encrypt a string and store that. But everything on the blockchain is public, so there's no place to store a decryption key. Even if the decryption key is off-chain, if it's ever brought on-chain to do decryption there, then everyone can immediately see it.

So encryption is only relevant of decryption is done off-chain. For example, you could encrypt something with a recipient's public key, and off-chain, that recipient could use their private key to decrypt it.