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Does anyone know how to calculate the originality signature of recent nxp product? It is an ECC signature. Any datasheet?
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Are you talking about what is described in AN11340?
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Yes. Knowing public and per-tag key how can i calculate the "validity"?
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We are able to obtain private key and we have the public key, the algo is ECC and parameteres are known: what is the math process to validate them ?
Last edited by asper (2015-03-11 17:00:27)
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it appears AN11341 is a secure download on nxp's website. my guess is it explains what you are looking for.
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The function is already implemented in some nfc android apps... I was only curious.
Anyway it is used also in recent ntag transponders, not only desfire.
Last edited by asper (2015-03-11 20:34:51)
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The function is already implemented in some nfc android apps...
Can you name these apps / provide links? The simpler the application the better.
I know there is an open source example hiding in github (or perhaps stackexchange?). I'll try to dig it up for you.
As marshmellow has already pointed out, AN11341 is a restricted download. You can request access to the document but I'm not sure how you'll go.
Some of my notes:
The 32-byte cryptographic signature is based on elliptic curve cryptography. This signature can be retrieved using the READ_SIG command and can be verified using the corresponding ECC public key in the PCD.
What is the public key?
Pub. N0.: US 2013/0342311 A1
https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US20130342311.pdf
ECDSA algorithm, curve secp128r1.
Using openSSL. Must be using ecdsa.h!
http://openssl.org/
Look at Utilities.java in the 'MIFARE SDK Lite'
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The app is nfc tag info.
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The app is nfc tag info.
NFC tag info uses the same technique (similar code) as Utilities.java.
Check out http://www.mifare.net/en/products/mifare-sdk/mifare-sdk-lite/#download
You might want to create a fake email address so you can register and download the SDK.
Look for:
checkEcdaSignature(String paramString, byte[] paramArrayOfByte1, byte[] paramArrayOfByte2)
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Thank you very much ! I knew "you are the right man" !
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