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I'm trying to understand article about calculate probe request 6-byte footprint.

this what it say:

First, a 6-byte footprint is initialized to zero (00: 00: 00: 00: 00: 00). The IEs of each Wi-Fi probe are analyzed, as shown in Figure 5. Once the IEs of theWi-Fi probe are checked (avoiding using the ESSID, since it is always present and can be highly variable due to the fact that the same device can ask for several networks in a small period of time), a mini footprint is calculated. This mini footprint is a 1-byte value calculated as the checksum of the bytes contained in the analyzed IE. For those IEs that present highly variable values between probes issued from the same device, e.g., IE_DS_PARAM or IR_EXT_CAP, the mini footprint is calculated as the code of the IE itself (003 for IE_DS_PARAM, 07F for IE_EXT_CAP, etc.). Sequentially, each time a mini footprint is obtained, its value is added to that of the content of the next byte of the footprint, and the mask 0xFF is applied to it. If the number of mini footprints is greater than 6, it begins again with the first element of the footprint, and so on

I have did all the calculation and I get this (same as the example in the article):

The sequence of IE codes 01:32:03:2D:7F:6B:DD

Length of each IE in hexadecimal 04:08:01:26:08:07:11

Values of each IE in hexadecimal 27:9E:06:86:C0:09:18

but I can't seem to understand how I get this footprint(the one in the example)

25:3E:12:FF:5D:4E

I took each value and mask it to 0xFF , have try to add the next value tries to add next value and then mask it to 0xFF but I can't get to the wanted answer

can someone guide me ? and show me how to calculate it ?

Thanks ,

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