Of course not downgrade, but custom OS with higher system signature.I believe it's theoretically possible to spoof a eShop update server. But I don't think you can use it to downgrade the console without first having a Arm11 kernel hack or access to the needed services as Arm11 normally verifies what it's installing is newer then what's being replaced. It doesn't normally allow you to downgrade and even a server spoof will not get around that if you don't have Arm11 at the least.
Okay, I thought some guy already have the private keys cracked. but what I mean is to replace sysnand.You need Arm9 access to fool sig checks. That or find a way to create valid signatures which requires gaining access to highly secret company data like the private keys. That is highly unlikely. It's a pipe dream to ever think you will be able to run a modified CFW natively on sysnand without using exploits.
Nope. Nintendo is the only people who can sign stuff. All we can do is run unsigned stuff via arm9hax. Other than that, there's really no point unless you are able to use homemenuhax to autoload kernel exploits to boot into a modified emunand. (I don't even think modifying emunand is even possible in a lot of ways. Merely minor stuff like tools and software, not anything near OS stuff.)Okay, I thought some guy already have the private keys cracked. but what I mean is to replace sysnand.
This happens as well, all tickets (even common ones) must be retrieved from the Nintendo servers, and non-common ones need proper signing from Nintendo as well. So even before issues with the app you're downloading's signature, you'd sooner have ticket issues.crazy stuff.
I believe 3ds verify some ticket or whatever with the server.