CUID tag suddenly not working

Hello.

Few monts ago I clonned a door tag into several sticks using Android and Mifare tools:
CUID Gen2 NFC ISO14443

https://es.aliexpress.com/item/1005006302595760.html?spm=a2g0o.order_list.order_list_main.15.5cf1194dRRtzTC&gatewayAdapt=glo2esp

I clonned 3 tags, and all of them worked perfectly. But now, three months later more or less, none of them work. I tried to read with Android smartphone and nothing happend, it’s as if they weren’t there. The same with three sticks. What happened? Have they a time limitation or something like that? It’s very strange that all three broke at the same time. The original key works.

THanks.

probably the door is making periodic changes to the tags when used, which would work with a single tag but now with 3 clones and the OG tag floating around.. to put it bluntly.. shits busted.

compare the memory contents of each gen2 tag and the original fob and I’ll bet they are different from the original.. hell the original is probably also been updated / changed if it’s been used regularly.

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Thanks for the answer .

The tags can not be read by the smartphone, it seems that are broken. But three tags more or less at the same time? I have another spare tags bought in the same order, and can be read. Very strange.

that is strange.. have a proxmark3 or diag tool you could use? have you tried using taginfo on your phone?

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I am using a smartphone and Mifare classic tools. When I clonned the tags I was able to read it again. But now the smartphone can not read the tags, even can not detect the tags.

please try to use taginfo on your phone and let me know what happens.. what errors display, if any.

also i looked at the wet inlays you referenced. these are very fragile and break very easily. they are designed for placing on protected surfaces that do not actually have direct physical contact with the phone or anything else really. if things were working then they all stopped working and your phone can’t really read any of them, not even with taginfo, then they are probably actually just physically broken.

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Thanks. I tried with taginfo and nothing. The smartphone do not detect the tags, so probably their are broken or deactivated.

I have a sticker stuck on the back of the phone, between the phone and the case, so it has always been very protected, and it does not work either.

Were you also using the original tag during this period?

I think somenmore testing is required.

How many of these spare tags do you own.

heres one quick example
if you have 2 spares

Copy original, using MCT, Write to both the spare tags.

With MCT Read to confirm and save each one.
Original
Test 1
Test 2

Using the compare tool on MCT, compare all 3 to each other.

if all 100% identical, put Test 1 on a shelf and dont touch it (This will be your control)

Next, use both your original and test 2 on your reader once.
Use MCT to compare to your saved copies.

no difference? continue to use Test 2 (and original?) as you had done previously.
IF, at some stage, test 2 stops working (if possible try to read and compare on MCT)
post results.
Also read the Original, and compare to the saved original.
any difference?
post results.
Then compare Test 1 to the current original.
Post results

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There is still plenty of opportunity to physically damage that tag. When I say they are fragile I mean they are extremely fragile. Regular use phone will put pressure on the tag as your case encounters bumps and squeezes and normal daily use. That will press on the tag stuck to your phone.

These tags are normally placed inside of objects that will completely isolate them from physical force exerted on them. They use a flip-chip design which means basically the silicon chip is carefully glued to the printed PET substrate using anti-ansiotropic conductive glue. That means it’s very sensitive to any kind of activity like bending the tag, pressing on the small black silicon dot from the outside, etc.

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Thnaks. I think they are broken, as you said. For me the strange thing is that they all went bad in about 3 days. I used them almost every day.

Thanks, good idea.

Fortunately I have 10 spares. I have cloned 2. I have compared both with the original tag and the data are the same. Both new sticks open the door correctly. I will put one of them in the back of the phone and I will use it. I am going to keep the other one (saved) without using it. We will se the results. Maybe takes some months.

Thanks.

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Hello.

Just in case anyone is interested. It’s been two months since I recorded the tags again, and so far they’ve been working fine. The one I have stuck on the back of my phone (between the phone and the case) is starting to fail. It seems the tags aren’t very good. Another one I recorded and stored without using is working properly. It looks like the tags degrade over time and stop working. These are the ones I used: https://es.aliexpress.com/item/1005006302595760.html?spm=a2g0o.order_list.order_list_main.15.5cf1194dRRtzTC&gatewayAdapt=glo2esp

Regards.

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