# Appendix C ARQC Response Message Format

This section gives the format of the data for the Online Processing Result / Acquirer Response message. This request is sent to the reader in response to an ARQC Message notification from the reader. The output is controlled by Property 0x68 – EMV Message Format. There are currently 2 selectable formats: Original and DynaPro. It is a TLV object with the following contents.

Original format:

```
F9<len>/* container for ARQC Response data */ 
    DFDF25 (IFD Serial Number)<len><val> 
    FA<len>/* Container for generic data */
        70<len>/* Container for ARQC */ 
                8A<len> approval
                Further objects as needed...
```

DynaPro format:

```
F9<len>/* container for MAC structure and generic data */ 
    DFDF54 (MAC KSN)<len><val>
    DFDF55 (Mac Encryption Type><len><val> 
    DFDF25 (IFD Serial Number)<len><val> 
    FA<len>/* Container for generic data */
            70<len>/* Container for ARQC */ 
                    8A<len> approval
Further objects as needed... (ARQC padding, if any, to be a multiple of 8 bytes)
CBC-MAC (4 bytes, use MAC variant of MSR DUKPT key that was used in ARQC request, from 
message length up to and including ARQC padding, if any
```


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