I think if the first digit is a '2' instead of a '1', that tells the reader to force a chip-only transaction. Or in other words, if you can write the mag data to a blank card, you can set that byte to what ever you want and have a field day. Unless there is some more validation at the bank level? Haven't tried personally.
Its in the "service code" field: https://en.wikipedia.org/wiki/Magnetic_stripe_card#Financial...
I think if the first digit is a '2' instead of a '1', that tells the reader to force a chip-only transaction. Or in other words, if you can write the mag data to a blank card, you can set that byte to what ever you want and have a field day. Unless there is some more validation at the bank level? Haven't tried personally.