HITAG 2
256-bit Crypto-1, vehicle immobilizers and access
Full Specifications
| Manufacturer | NXP |
|---|---|
| Frequency Category | LF 125 kHz |
| Frequency | 125 kHz |
| Protocol | Proprietary HITAG 2 protocol (not ISO/IEC 14443 or 15693). Emulation modes: Public Mode A (MIRO/µEM H400x compatible, Manchester), Public Mode B (ISO 11784/11785 animal ID, Biphase), Public Mode C (PIT compatible, Biphase) |
| Memory | 256 bits total (32 bytes) organized in 8 pages of 4 bytes each. 128 bits (16 bytes) user data in pages 4-7; 128 bits control/secret memory in pages 0-3. Serial Number: 32 bits. Secret Key: 48 bits. Password TAG: 24 bits. Password RWD: 32 bits. |
| Interface | RF contactless only (no battery, passive). Data transmission: half-duplex. Tag to reader: 4.0 kbit/s Manchester or Biphase coding. Reader to tag: 5.2 kbit/s BPLM (binary pulse length modulation). Modulation: ASK (amplitude shift keying). Absorption modulation from tag to reader. |
| Temperature Range | -40°C to +85°C operating, -55°C to +125°C storage |
| Form Factor | HT2 DC20 S20/F: Stick transponder, 12 x 6 x 3 mm, epoxy resin encapsulated (black), IP67 rated |
| Security | Mutual authentication with proprietary 48-bit crypto stream cipher. Password mode (32-bit Password RWD, 24-bit Password TAG). Crypto mode (48-bit secret key, encrypted data transmission). Selective read/write protection per page via configuration byte. One-time programmable (OTP) lock bits for pages 1, 2, 3 (Bit 6 and Bit 7 in configuration byte). User-defined write protection. Authentication duration: ~36 ms. |
Engineering Brief
The HITAG 2 (HT2 DC20 S20) is a 125 kHz LF passive RFID transponder with 256 bits of EEPROM (128 bits user, 128 bits control/secret) organized in 8 pages. It supports mutual authentication using a proprietary 48-bit stream cipher in crypto mode or 32-bit password authentication in password mode, enabling secure bidirectional read/write communication. The chip offers flexible operation modes including crypto, password, and three public (read-only emulation) modes compatible with legacy systems (MIRO, ISO 11784/11785 animal ID, PIT). Key features include selective page write protection, OTP lock bits, multi-tag operation via HALT command, 10-year data retention, >100,000 write cycles, and operation from -40°C to +85°C, making it ideal for automotive immobilizers, secure access control, and industrial identification.
Typical Applications
- Vehicle immobilizers and automotive access control
- Secure access control and identification systems
- Contactless smart card applications with password or crypto protection
- Animal identification (ISO 11784/11785 emulation mode)
- Backward-compatible replacement for legacy read-only transponders (MIRO, µEM H400x, PIT)
- Multi-tag anti-collision applications (HALT function)
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