Mifare Classic 1K Memory Map Viewer: Understand Every Sector and Block of Your Card
1What Is Mifare Classic and Why Visualize Its Memory?
Mifare Classic is one of the most widely deployed contactless smart card technologies in the world. Developed by NXP Semiconductors (formerly Philips), Mifare Classic cards operate at 13.56 MHz (HF, ISO 14443 Type A) and are found in billions of transit cards, access control badges, loyalty cards, and campus IDs worldwide. The '1K' in Mifare Classic 1K refers to 1 kilobyte (1024 bytes) of user-accessible memory, organized in a very specific structure that requires understanding to work with effectively. Unlike NDEF tags where data is freely stored, Mifare Classic has a rigid memory organization with sectors, blocks, authentication keys, and access control bits that govern who can read or write each portion of the card. This tool takes the raw hex dump of a Mifare Classic 1K card — a 2048-character hex string representing all 64 blocks of 16 bytes each — and displays it as an organized, color-coded table showing sectors, block types, data content, and the parsed keys and access conditions in every sector trailer. This is an essential tool for: NFC/RFID system integrators who need to analyze card content, security researchers studying Mifare Classic vulnerabilities, developers building access control or transit systems, and students learning about contactless smart card architecture.
2Mifare Classic 1K Memory Architecture Explained
The Mifare Classic 1K card has a precisely defined memory organization that every developer and integrator must understand. Total capacity: 1024 bytes organized as 16 sectors (Sector 0 to Sector 15). Sector structure: Each sector consists of 4 blocks of 16 bytes each. Blocks are numbered 0 to 63 globally (absolute block numbers), or 0 to 3 within each sector (relative block numbers). Data blocks (blocks 0, 1, 2 within each sector): These blocks store actual data. Each block is 16 bytes. The application data (access control records, transit balance, etc.) is stored here. Sector Trailer (block 3 of each sector): The last block of every sector is the Sector Trailer — it does NOT store application data. Instead, it contains the security configuration for that sector: bytes 0–5: Key A (6 bytes, 48 bits). bytes 6–9: Access Bits (4 bytes, but only 3 bytes used for access conditions plus one byte 'gpb' for general purpose). bytes 10–15: Key B (6 bytes, 48 bits). Key A is always unreadable — reading the sector trailer returns zeros or masked bytes in the Key A position. Key B may be used as additional data storage if the access bits are configured accordingly. Special case — Sector 0, Block 0: The very first block (absolute block 0) is the Manufacturer Block. It contains the card's UID (4 or 7 bytes), BCC (Block Check Character), SAK, ATQA, and manufacturer data. On genuine Mifare Classic cards, this block is write-protected by the manufacturer and cannot be overwritten.
3Real-World Applications: Where Mifare Classic Cards Are Used
Despite its age and known security vulnerabilities, Mifare Classic remains extraordinarily widespread due to the massive installed base of infrastructure built around it. Public transit systems: Some of the world's most famous transit cards use or have used Mifare Classic 1K — including the original OV-chipkaart (Netherlands), the early Oyster card (London), and transit systems in many cities across Asia, Eastern Europe, and Latin America. The balance and trip data are stored in the data blocks, with the sector trailer keys protecting access. Access control systems: Millions of office buildings, hotels, university campuses, and secure facilities use Mifare Classic cards for door access. The card UID alone is used in many legacy systems (a fundamentally insecure approach), while better implementations store encrypted credentials in the data blocks protected by sector keys. Loyalty and membership cards: Many retail chains, libraries, gyms, and clubs distribute Mifare Classic cards for loyalty programs, storing member ID and points balance on the card itself. Campus cards: Universities issue Mifare Classic-based student IDs that double as library cards, cafeteria payment cards, and dormitory access cards — all stored in different sectors of the same 1K card using the MAD (Mifare Application Directory) standard. Parking and vending: Parking systems and vending machines that accept contactless payment often use Mifare Classic with stored value on the card. For new deployments, NXP recommends Mifare Plus (backward compatible but with AES encryption) or Mifare DESFire for higher security requirements.
4Access Bits, Sector Trailers, and Security Model
The access bits in the Sector Trailer are the most complex and critical part of the Mifare Classic security model. Understanding them is essential for anyone configuring or analyzing Mifare Classic cards. Access bits structure: The 3 access bytes (bytes 6, 7, 8 of the sector trailer) contain 4 groups of 3 bits each (C1, C2, C3) for each of the 4 blocks in the sector (3 data blocks + the trailer itself). These bits are stored in a redundant format with their complements to detect errors: bytes 6-7 store the complement values, byte 8 and part of byte 7 store the actual values. Access conditions for data blocks: Each combination of C1C2C3 defines different read/write permissions for Key A, Key B, and the 'never' condition. The default transport configuration (bytes 6-9 = FF 07 80 69) allows full read/write access with Key A. A typical production configuration restricts write access to Key A only and allows read access with either key. Access conditions for the Sector Trailer: The trailer itself is also protected by access bits. Depending on the configuration, Key A may be readable or unreadable, and which key is required to modify the keys and access bits can be configured. Mifare Classic best practice is to make Key A unreadable after personalization. Known security issues: Mifare Classic uses a proprietary stream cipher called Crypto-1. This cipher was reverse-engineered in 2008, leading to practical attacks — notably the Dark Side Attack and the Nested Authentication Attack — that allow recovering sector keys without knowing them beforehand, using nothing more than a commodity NFC reader. This is why Mifare Classic should NOT be used for new high-security applications.
5How to Get a Mifare Classic Dump and Tools for Analysis
To use the Mifare Memory Map viewer, you need a full 1024-byte hex dump of the card. Here is how to obtain one using common tools. Using NFC Tools Pro (Android): The Pro version of NFC Tools can read Mifare Classic sectors if you provide the correct keys. Go to 'Advanced' → 'Mifare Classic' and attempt to read each sector. The app tries default keys (0xFFFFFFFFFFFF, 0xA0A1A2A3A4A5, etc.) automatically. Using MIFARE Classic Tool (Android, free, open source): This dedicated app tries a built-in key dictionary against each sector. Once sectors are unlocked, it can dump the entire card to a .mct file containing the hex data in a sector-by-sector format. Convert the .mct to a continuous hex string by removing sector headers. Using Proxmark3: The Proxmark3 is the professional tool for Mifare Classic analysis. Commands include 'hf mf autopwn' to automatically find all sector keys and dump the card. The output is a .bin file of exactly 1024 bytes that can be converted to 2048 hex characters. Using ACR122U with libnfc or mfoc: On a computer, use an ACR122U USB NFC reader with the mfoc (Mifare Online Cracker) tool to attempt key recovery using nested authentication attacks. Output is a 1024-byte binary dump. Formatting the dump for this tool: The tool expects exactly 2048 hexadecimal characters (no spaces, no line breaks, no sector headers). If your dump tool adds spaces or newlines between bytes, remove them before pasting.
FAQFrequently Asked Questions
What are the default keys for Mifare Classic cards?
New Mifare Classic cards from the factory (transport configuration) typically use 0xFFFFFFFFFFFF for both Key A and Key B on all sectors. Other common default keys used by specific manufacturers or systems include: 0xA0A1A2A3A4A5 (used by some NXP applications), 0xD3F7D3F7D3F7 (used in Mifare Application Directory sectors), 0x000000000000, and 0xB0B1B2B3B4B5. Tools like MIFARE Classic Tool for Android maintain a dictionary of hundreds of known keys and try them automatically. If a sector uses a custom key set by the system operator, recovering it requires exploiting Mifare Classic's Crypto-1 vulnerabilities using tools like Proxmark3.
Can I write data back to the Mifare Classic card using this tool?
No, this tool is read-only and visualization-only. It analyzes a hex dump that you provide and displays the memory structure — it does not communicate with any NFC hardware. To write data back to a Mifare Classic card, you need an NFC reader/writer (ACR122U, Proxmark3, or an Android device with Mifare Classic support) and the correct Key A or Key B for the sector you want to write to. Unauthorized writing to Mifare Classic cards (such as transit cards or access badges you do not own) is illegal in most jurisdictions.
What is the MAD (Mifare Application Directory)?
The MAD is a standardized directory stored in Sector 0 (and optionally Sector 16 on 4K cards) that maps which sectors are used by which applications. It uses a predefined format (NFCID application code 0xE103 for Mifare Application Directory) to register application identifiers (AIDs) with their corresponding sectors. This allows multiple independent applications (transit, loyalty, access control) to coexist on a single Mifare Classic card without conflicts. The MAD sector (Sector 0) uses Key A = 0xA0A1A2A3A4A5 in the standard configuration. This tool displays the raw hex content of all sectors, including Sector 0, so you can identify MAD entries manually.