If you want to cheat your spouse, you must do it at beginning of your marriage life as according to law, assets and properties created during a marriage belong to two people, a wife and a husband and it will be separated 50/50 if there was no special marriage contract before.

I think it does not make sense to cheat your spouse and if you don't trust her or him at beginning of your marriage, I don't think it's a good person who you can live with. Hence, let's think deeply that why you want to start that marriage life.

If you trust him or her, let's think of different thing, an inheritance plan of your couple's bitcoin.

I aggree with you that such cheating can have problems with government, not only with your spouse.