Like launchd says, a really good crypto programmer could put the correct bits back into place after the modifications and that may fool the VW scanner, but to date, nobody has successfully done that.
Only if the system is using a compromised hashing algorithm, such as SHA-1. Since the tech is relatively new, I would say that is unlikely. I'm still reading over the patents but so far I don't see anything about encryption of map data, if there is encryption it's more likely this is being accessed with the actual decryption key. My guess would be they are all encrypted with the same key, otherwise service would be a nightmare. This is far more likely than the encryption key being cracked, that kind of thing generally does not happen anymore unless the encryption is intentionally weak/vulnerable.
If stock maps are protected with a recorded hash, there's no reason to encrypt them, especially not with a weak encryption. Hashes are not reversible, you can't be a really good modder who fools one, that's like mixing up playdoh and then trying to separate it again. Hashing produces a unique string (mixed playdough) based off of the data that was submitted, submitting different data means a different string, period. If the point of the hash is to TD1 people for modifying the ECU, why encrypt that information and make it harder for people to TD1 their cars? An exposed hash is not vulnerable.
There has to be some side counter for sure who is tracking modifications.
I would agree, if the original maps have encryption that is "cracked" all that needs to be done at that point is re-encrypting that data with the same method VW used originally. Even if it's not cracked, that unmodified data should be able to be sent back to the ECU and have the same hash.
I have two theories for each scenario:
1. If encryption exists, it has never been cracked. This matches what tuners have said with their stock maps being "like-stock" but not OEM. Meaning they have the ability to flash new maps to the ECU, but no way of interpreting, modifying, or recreating the old data because it remains encrypted.
With this said, how does the Cobb default map work? I was under the impression the initial flash from a Cobb copies the map data from your car so it can add it back later? If it is copying encrypted data, and simply spitting that data back onto the ECU for the reflash, that data would be identical (same hash) unless a counter exists at some point to change that data in some way, thus changing the hash, and causing a TD1.
2. If encryption is cracked and we can see the true original map, there's still something modifying the hash in the ECU to alert VWoA even though we have that identical data to send back to the ECU. A simple +1 counter tucked away in the ECU code somewhere that changes some data every time someone remaps the ECU, meaning a completely different hash, i.e. td1. Thing is, if the OEM data was unencrypted ("cracked") and thus readable in plain text, someone would have found that already. So I'm thinking number 1 is more likely, but I need to know what is actually happening with the Stock map process to give a better answer.