pilkington
Re:Ask HN: Why are credit card chip readers so slow?
on Friday June 30, 2017 @08:35PM (#14674519)
You can decipher some of the fields printed on the receipt using https://tvr-decoder.appspot.com. The acronyms are from the EMV specs (https://www.emvco.com/specifications.aspx?id=223, probably book 3)
Eg. TVR: 0000008000 (Byte 4 Bit 8) Transaction exceeds floor limit
Floor limit being the $/EUR/whatever amount that could be approved offline.
The 2 in the diagram appears to be pointing at a cleartext credit card number.