ISO 8583 Bitmap: How to Decode Message

ISO 8583 financial message type is ‘0200’. This message has a lot of bits as per ISO 8583. This format has Five parts. I am sharing in this post how to decode or parse the message in simple steps.


ISO 8583 specification is most popular in all payment transactions. The financial ISO 8583 Message is X2XX. That means the second position ‘2’ says that it is a transaction that amount will debit from your Bank account. All the Debit card transactions come under this type of message.

Snippet from ISO 8583

ISO 8583 message

How the ISO 8583 Message Has Header and Details

Message type indicator (MTI)

The MTI consists of four numeric digits that specify the version of the ISO8583 standard, message class, message function, and message origin. Three versions of the standard exist in 1987, 1993, and 2003. The combination of the four MTI fields specifies the type of interchange message that is being transmitted.

Typically, applications use the MTI to determine whether the message requires a response and the format of the response:

  • The values to include in the MTI
  • The Message Data fields to include in the reply

One or more bitmaps

A message always includes a primary bitmap whose individual bits indicate which of the later fields are present in this particular message instance. The primary bitmap specifies whether fields 1 – 64 are present.

If a secondary bitmap is also included, it specifies whether fields 65 – 128 exist. The standard also provides for a tertiary bitmap, which is rarely used. The bitmaps can appear in 8-byte ‘packed’ format or 16-byte ‘unpacked’ format.

Message Data fields

Message Data fields are defined by the ISO8583 standard and contain information about the transaction, such as amounts, dates, times, and country codes. Organizations that use ISO8583 often customize these fields.

ISO 8583 Sample Message Format

ISO 8583 Sample Message Format

ISO Message Format contains, four parts. These parts are :

1: Custom Headers

2: MTI

3: Primary Bitmap

4: Secondary Bitmap

5: Details

ISO 8583 Bits Vs Bitmap

ISO Bit NumberBitmap Hex ValueBit positions
1, 2, 3, 4, 5E011111000
9,10C011000000

In the first row, first, second, third, fourth, and fifth bits are ‘1’. That means those bits are present. You can find general ISO 8583 Bits here.

Binary Bit calculaor

The Tool to calculate Bits and Bitmap hex value you can find here.

References

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Author: Srini

Experienced software developer. Skills in Development, Coding, Testing and Debugging. Good Data analytic skills (Data Warehousing and BI). Also skills in Mainframe.