How can I share private client information among users in different chains without storing it to state?

Hey guys
What is the best way to share sensitive information among two different chains without committing it to the state?

For example I got used A in chain A to send his phone number to user B in chain B. The user A and user B are clients.i would not want this phone number to be commited. Nor would I want any intermediary node to look at it.

The data must be sent to user B in a p2p way.

I think the NYM Project might know the answer to this.