NTAG213F/216F
NXP Semiconductors
NFC Forum T2T IC with 144/888 bytes user memory and field detection
8.9.2 Limiting negative verification attempts
To prevent brute-force attacks on the password, the maximum allowed number of
negative password verification attempts can be set using AUTHLIM. This mechanism is
disabled by setting AUTHLIM to a value of 000b, which is also the initial state of
NTAG21xF.
If AUTHLIM is not equal to 000b, each negative authentication verification is internally
counted. As soon as this internal counter reaches the number specified in AUTHLIM, any
further negative password verification leads to a permanent locking of the protected part
of the memory for the specified access modes. Independently, whether the provided
password is correct or not, each subsequent PWD_AUTH fails.
Any successful password verification, before reaching the limit of negative password
verification attempts, resets the internal counter to zero.
8.9.3 Protection of special memory segments
The configuration pages can be protected by the password authentication as well. The
protection level is defined with the PROT bit.
The protection is enabled by setting the AUTH0 byte to a value that is within the
addressable memory space and that is at least the first page address of the configuration
pages (29h for NTAG 213F or E3h for NTAG 216F).
8.10 Originality signature
NTAG21xF features a cryptographically supported originality check. With this feature, it is
possible to verify with a certain confidence that the tag is using an IC manufactured by
NXP Semiconductors. This check can be performed on personalized tags as well.
NTAG21xF digital signature is based on standard Elliptic Curve Cryptography, according
to the ECDSA algorithm. The use of a standard algorithm and curve ensures easy
software integration of the originality check procedure in an application running on a NFC
devices without specific hardware requirements.
Each NTAG21xF UID is signed with a NXP private key and the resulting 32-byte signature
is stored in a hidden part of the NTAG21xF memory during IC production.
This signature can be retrieved using the READ_SIG command and can be verified in the
NFC device by using the corresponding ECC public key provided by NXP. In case the
NXP public key is stored in the NFC device, the complete signature verification procedure
can be performed offline.
To verify the signature (for example with the use of the public domain crypto library
OpenSSL) the tool domain parameters shall be set to secp128r1, defined within the
standards for elliptic curve cryptography SEC (Ref. 7).
Details on how to check the signature value are provided in following application note
(Ref. 5). It is foreseen to offer not only offline, as well as online way to verify originality of
NTAG21xF.
NTAG213F_216F
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2013. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 3.1 — 28 August 2013
262231
31 of 56
NXP [ NXP ]
