I、The CUID card, full name Card Unique Identifier (Card Unique Identifier), is a rewritable contact IC card based on 13.56MHz high-frequency NFC technology. Its core feature is the built-in unique identifier (UID) that can be modified multiple times. It belongs to the passive tag under the NFC technology system (following ISO/IEC 14443 Type A/B protocol), rather than an independent card type. Essentially, it is an "NFC card with flexible UID modification function".

II、 Core Technical Characteristics of CUID Card

UID can be repeatedly rewritten:

Unlike traditional M1 cards (UID cannot be modified after factory production) and FUID cards (the 0 sector can only have one write opportunity), the 0 sector (the key area storing the UID) of the CUID card supports unlimited modification. It can be used without locking the card, avoiding card due to accidental writing.

No backdoor， security verification standard：

Unlike UID cards with system backdoors， the 0 sector of the CUID card needs to be written through regular password verification. The operation logic of other sectors is consistent with standard M1 cards， balancing flexibility and basic security.

Anti-shielding and high compatibility：

It has built-in anti-shielding function， capable of dealing with "anti-replica card readers" after property upgrades. The adaptation rate for door access systems is approximately 90%， solving the problem of "rolling passwords" in most residential areas， and compatible with mainstream NFC reading devices (such as mobile phone NFC， MIFARE Classic Tool software).

Structure and material：

The core consists of an RFID chip (including read-only UID storage area + read-write data area) and an antenna. The shell is mostly made of PVC material, with a standard size of 85×54mm (consistent with bank cards), thickness of 0.76-0.84mm, and supports customized printing.

Typical application scenarios of CUID card

Access control and security domain：

Replace lost/damaged access cards and elevator cards, compatible with non-high security level access systems in old residential areas / commercial areas， solving the problem of "old card failure after property upgrade reader" (equipment debugging and testing)：

Used for NFC device compatibility testing (such as mobile phone NFC function verification)， access system debugging， can repeatedly modify UID to simulate different cards， reducing testing costs (daily convenient scenarios)：

When the mobile phone does not have NFC function， combine CUID card + external reading device to achieve access simulation；

Used in patrol systems， attendance， parking management， campus one-card (low security requirement scenarios)

Personalized customization：

Support CMYK full-color printing， can be made into work certificates， membership cards， business cards， etc.， balancing identification and function