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Definition

PARes - Payer Authentication Response

Is one of the messages defined in the 3DS authentication workflow, and contains the results of the payer authentication. It is the response to the PAReq (Payer Authentication Request).

The PARes has an XML structure with the information from the response of the authentication, and it contains a digital certificate as a sign of authenticity.

The PARes is transmitted in compressed messages and encoded in Base64.

This is a 3DS 1.x message, and in 3DS 2.x the equivalent to the PAReq/PARes messages are the following:

Content

Relevant fields contained in the PARes

• version: Exact version of 3DS

• acqBin: Acquiring Bank’s Identification Number (First six digits)

• merID: Merchant ID

• xid: Transaction Identifier - Unique Identification number which is sent to the ACS and which is included in the PAReq (Payer Authentication Request) message.

• pan: Personal Account Number - Card number

• status: PA Transaction Status - Result of the authentication transaction.

  • Y: Authentication correct.

  • N: Authentication canceled or authentication failure. Transaction denied.

  • U: Incomplete authentication, independent of reason.

  • A: Authentication attempt.

• eci: Electronic Commerce Indicator - Indicates the outcome of the authentication. (More information on the ECI can be found here ECI)

• cavv: Cardholder Authentication Verification Value - 3DS Authentication verification token generated by the issuer during the authentication process.

The authentication verification token have distinct names depending on the card issuer:

Examples of these fields within the PARes

Processed

The PARes is transmitted in Base64, and to obtain the information contained therein requires two steps:

• Decode the text in Base64 to obtain the compressed binary in ZLIB format

• Decompress the binary ZLIB to obtain the XML (Deflater Java Doc)

Python code to decode the PARes message

Examples

Examples of text from a PARes in Base64 and its equivalent in XML

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