Let's say I have an encrypted message. I want to make it so that someone is able to decrypt it. The only way of giving it to them is online. For the purposes of this question, I can't call, mail or meet them in person.

I want to ensure that only they are able to decrypt it. I know that the method of communication (whatever you want it to be) isn't monitored yet, but the message could be read at any time. How would I do this?

This is all 100% hypothetical, I have no plans of doing any illegal activities

Let's say I have an encrypted message. I want to make it so that someone is able to decrypt it. The only way of giving it to them is online. For the purposes of this question, I can't call, mail or meet them in person.

I want to ensure that only they are able to decrypt it. I know that the method of communication (whatever you want it to be) isn't monitored yet, but the message could be read at any time. How would I do this?