interpretation of sizes of fields (bitmap) ISO8583

Question

What should be the correct interpretation for the sizes of each bit represents :

Bitmap  attribue  length in bytes
1       b 1       16 (every two, representing a binary byte)
52      b 64      ???
64      b 64      ???
65      b 1       ??? (will be 16 too ?)
96      b 64      ???
128     b 64      ???

Need to implement the treatment for this information.

Tanks.

Answer 1

The docs for all fields is e.g. here. 1 is "Bit Map Extended", 52 is "Personal Identification number data", 64 is "Message authentication code (MAC)", 65 is "Bit map, tertiary", and so on (though the lengths are not as you give them -- see the same Wikipedia page I've already pointed to, it's quite informative).

If you need the authoritative reference, you'll need to splurge 252 Swiss Francs to ISO for a PDF or paper copy of the official standard, of course.

Answer 2

There is lots of references on interpreting ISO-8583 out there, even Wikipedia's article is pretty good, though a quick Google search will also find you many publicly available ISO-8583 specifications of different variants.

I own an authoritative copy of ISO-8583 and do not find it especially useful, actually I almost never look at it as everyone has a variant of it and no one implemented exactly to ISO as it allows for some private and national use.

ISO Field: 1 = Secondary/Extended Bitmap; always will be 16 but may be BCD'd. 52 = Personal Identification Number Data b64; 16 hex digits not present in all messages and should be cleared once validated. 64 = Message Authentication Code b64; hex 16 if it is actually used. 65 = Tertiary Bitmap (HEX 16 but may be BCD'd) 96 = Message Security Code b64; but I've always seen it between 4-8 ascii printable characters. 128 = Message Authentication Code b64; hex 16 if it is actually used.

Important: Secondary bitmap will not exist unless there are actually data elements in its range of coverage, an all 0 value is invalid. A Tertiary bitmap cannot exist unless a secondary bitmap is also present. Bits 001-064 Primary Bitmap Bits 065-128 Secondary/Extended Bitmap Bits 129-193 Tertiary Bitmap (Rarely Used)

I'd be curious as to what type of message you are trying to do with just a PIN code and a message security code message security code is usually accompanied by an action code in another data element and a payload of the action throughout other data elements.