3 Notation

It is important to be clear on the difference between binary, decimal and hexadecimal notation.

For consistency, Thredd follows EMV notation. https://www.emvco.com/. For a full list, refer to EMV book 4.3 section 4 ‘Abbreviations, Notations, Conventions and Terminology’.

The following table summarises the notation used by Thredd:

Notation	Description
0 to 9	Decimal digits
‘0' to '9' and 'A' to 'F'	Hexadecimal characters. These will always be in single quotes
AC	Application Cryptogram The Application Cryptogram is an encrypted value generated by the EMV chip card during a transaction. It is used for transaction validation, fraud prevention and data security. here are several types of application cryptograms used in EMV transactions: ARQC, ARPC and AAC.. Defined by EMV, and in EMV tag ‘9F26’.
00000000	8 binary bits. Most significant bit is on the left, least significant on the right. In accordance with EMV: Bit 8 = Most significant (top) bit in the byte Bit 1 = Least significant (bottom) bit in the byte
0	A single binary bit, value 0
1	A single binary bit, value 1
Byte numbers	If a parameter is made up of bytes, then: Byte 1 is the first byte Byte 2 is the second byte, and so on.
Profile	This describes one particular complete set of configuration settings for a chip card. For example, if all the chip cards pre-configured data was the same for all your cards, you would only need 1 Profile.
RFU	Reserved for Future Use
TLV	Tag Length Value
Tag	The tag part of TLV
Template	Some tags are held inside Templates. There can be many templates holding different values of the same items. For example, the tag ‘5F2D’ (language preference) is held inside the FCI Proprietary Template ‘A5’, which is held inside the FCI Template ‘6F’. There may be many different FCI Templates on the card, hence many different ‘5F2D’ values, one for each different template. See EMV Book1 section 11.3.4 (SELECT command response APDU data)