Sharing an verifiable secret message in a contract

I would like to hear your opinion on my idea to share a proof of a secret message in a contract, that users can verify later in a second phase when the message will be revealed.

If the message is a random piece of text, you could easily store a hash of the message as a proof and when the secret message is revealed, compare both hashes to verify its validity. However if the message is just a word or a number that can be easily included in a dictionary, you can have as well a collection of hashes indexed for every word/number in the
dictionary and you will be able to find the corresponding secret message.
The proposed solution will use symmetric cryptography (Fernet) to encrypt off-the-chain the message and store a hash of the encrypted message in the contract.

On a different phase when the secret message will be reveled, the full encrypted message and its secret key will be shared as well in order to verify the initial proof provided. Decrypting the message off-the-chain and comparing its hash to the initial proof will be enough to verify it.

Is there any other way am I missing?