How to Decode TLV Quickly

In TLV, the format is Tag, Length, and Value. The TLV protocol needs this type of data. Here you will know how to decode TLV data. According to IBM, TLV data is three parts. The tag tells what type of data it is. The length field denotes the length of the value. The Value-field denotes the actual value.

Structure of TLV.

TLV comprises three field values. 

1. Tag
2. Length
3. Value

How to Decode TLV

EMV formulated different tags. They have their meanings. Usually, the Tag and Length together takes 1 to 4 bytes.

1. The Best example for TLV.

In the below example, you can find the sample TAG, LENGTH, and VALUE fields.

[Tag][Value Length][Value] (ex. "9F4005F000F0A001")

where, Tag Name = 9F40

Value Length (in bytes) = 05 

Value (Hex representation of bytes. Example, "F0" – 1-byte) = F000F0A001

In the above message, tag 9F40 has some meaning designed by EMV company. Here you can find a list of EMV Tags.

2. How to read the TLV

Tag: 1 or 2 bytes.

Length: Length of the Value.

F0-00-F0-A0-01 ==> 5 Bytes

The 'F0', for example, is the HEX value of length '1' byte. So the total length of the value '5' bytes.

Keep Reading

1. Tag Length Value Tutorial