Thank you for breaking all of that down. Lol I was wondering why a Gen1a magic card I purchased from one vendor didn’t work on my front door, while the one I got from another did. I guess it’s kinda hard to standardize something that’s not supposed to exist.
I found a document from NXP Semiconductors that explains what BCC bits are. It says it’s a calculated value, so I don’t think people are likely to fuck them up. I really have no idea though.
I’m waiting on a Gen1a & Gen2 a to arrive from the company I linked to previously. Is there any way to check if they match the chips you use? I have a Proxmark3 and the tag info app.