解析iso8583消息时出现问题

Question

I've download code from here https://github.com/vikrantlabde/iso8583-Java and after some modifications I'm parsing almost fine my fields.... I defined the schema like this:

ISOSCHEMA.put("1","BITMAP");
ISOSCHEMA.put("2","NUM-2-19-0_0");
ISOSCHEMA.put("3","NUMERIC-0-6-0_0");
ISOSCHEMA.put("4","NUMERIC-0-12-0_0");
ISOSCHEMA.put("7","NUMERIC-0-10-0_0");
ISOSCHEMA.put("11","NUMERIC-0-6-0_0");
ISOSCHEMA.put("12","NUMERIC-0-6-0_0");
ISOSCHEMA.put("13","NUMERIC-0-4-0_0");
ISOSCHEMA.put("22","NUMERIC-0-3-0_0");
ISOSCHEMA.put("23","NUMERIC-0-3-0_0");
ISOSCHEMA.put("35","NUM-2-37-0_0");
ISOSCHEMA.put("41","FCHAR-0-8-0_0");
ISOSCHEMA.put("49","FCHAR-0-3-0_0");
ISOSCHEMA.put("55","NUM-3-999-0_0");

The problem is the field 55 that is a binary field. The standard documentation says it:

55 Reserved ISO B 255 LLLVAR (ISO DOCUMENTATION)

I'm having an error parsing a string that has the bitmap turned on for the field 55.

I'm having from the output: 820200409F36020004950500000000009A031409039C01005F2A020 978 9F02060000000005009F03060000000000009F10201F430200200000000000000000045895000000000000000000000000000000009F260840D26C4BA5577CFB9F2701809F370443DD7E879F1A0202509F3303E0B0C8

But I expect: 820200409F36020004950500000000009A031409039C01005F2A020 124 9F02060000000005009F03060000000000009F10201F430200200000000000000000045895000000000000000000000000000000009F260840D26C4BA5577CFB9F2701809F370443DD7E879F1A0202509F3303E0B0C8

The length of the iso payload converted is highly different too...

The program output is:

What I expect is: 30313030723806002080820031363635343332313131323233333434353530303030303030303030303030303030303131303136313833343236303032333934313333343330313031363037313030313337363534333231313132323333343435353D33313130323230303039323833303031303130323834303137343039313234313135820200409F36020004950500000000009A031409039C01005F2A0201249F02060000000005009F03060000000000009F10201F430200200000000000000000045895000000000000000000000000000000009F260840D26C4BA5577CFB9F2701809F370443DD7E879F1A0202509F3303E0B0C8

One advice is: I have to make the explicit conversion to hex from the resultant byte[] and viceversa. It is:

String isoMessage = ISOUtil.hexString(packIsoMsg("0100", isofields).getBytes());

And:

unpackIsoMsg(new String(ISOUtil.hex2byte(isoMessage), "UTF-8"));

What about the definition of this kind of fields in this class? I'm really a newbie with the standard but I arrived here because jpos doesn't work in an Android environment. Also I'm confused with the last mentioned conversion to hex.

Any help is really appreciated... Kind regards.

Answer 1

DE55 is defined as a Tag-Lag-Value (TLV) field that is not in the normal Binary / text / or numeric packed format you see the rest of ISO-8583 messages typically but is in ASN.1 BER-TLV / X.690-0207 format.

Unless you account for the BER-TLV you will not successfully unpack DE55 unless it is for non-EMV/Tokenization purposes. It threw me at first as well as I was thinking something more straight forward. Be aware that sometimes the field transport format is actually longer in this format than the original plain text or other binary data output so it is not the most efficient.

There are a couple of other fields depending on the ISO specification may also use BER-TLV but DE55 is the industry standard field to use BER-TLV for EMV functionality replacing DE55's previous use as a generic and rarely used 'fee field'.

The ISO-7816 specification its ISO-8583 use in detail for EMV and Tokenization, as well there are other references and quick guides out there if you are just looking for something not so in-depth. All volumes of the ISO-7816 specification can be found openly on the internet for free, or can be purchased directly (spendy) from the ISO organization if you want them in the plain ISO format.

I am not familiar with the specific JAVA Git you referenced but this one has a help page on how to use BER-TLV. Oracle also has a page on dealing with BER-TLV here . BinaryFoo has a Git available as well.

For the purposes of initial testing, if your data is just test data (DO NOT USE PRODUCTION DATA!) you can use http://www.emvlab.org/tlvutils/ to verify your results. Which when I input your inputs it kicks out your expected output.

Answer 2

what is the field defined by sender in field 55.Assign the same in unpacking.If they are sending string it should be LLLVAR. when sending ISO message header must be in hex format.hence they convert bytes to hex.

Answer 3

From the looks of it, you consider 5F2A020978 as wrong whereas you expect 5F2A020124. The EMV tag's 5F2A data (with length 02) is the transaction currency code . This means your transaction is performed in EURO currency instead of Canadian dollar as you expect. You can find a currency code list here .

Hope this helps.