USING MIFARE CLASSIC TAGS VERSION

Transcription

1 USING MIFARE CLASSIC TAGS VERSION

2 U s i n g M I F A R E C l a s s i c T a g s P a g e 2 TABLE OF CONTENTS 1 Overview Required Reading Document Scope MIFARE Features Accessing Memory MIFARE Classic 1k Memory Structure MIFARE Classic 4k Memory Structure MIFARE Classic Access Control Options Select Tag (0x0101) Command Description Command Structure Flags Fields Example 1 Selecting with Auto-detect Tag Type Request Response Example 2 Starting a Tag Session using the TID Request Response Authenticate Tag (0x0201) Command Description Command Structure Flags Fields Example 1 Authenticating MIFARE Classic Tags Request Response...12

3 U s i n g M I F A R E C l a s s i c T a g s P a g e 3 4 Read Tag Data (0x0102) Command Description Command Structure Flags Fields Example 1 Reading MIFARE Tag Memory Request Response Example 2 Reading different blocks within the authenticated sector Request Response Example 3 Reading the sector trailer Request Response Write Tag Data (0x0103) Command Description Command Structure Flags Fields Example 1 Writing a block of data Request Response Revision History...16

4 U s i n g M I F A R E C l a s s i c T a g s P a g e 4 1 Overview 1.1 Required Reading This document assumes you have read and are familiar with the SkyeTek Protocol V3 Reference Guide and the SkyeTek Protocol V3 Basic Examples application note. 1.2 Document Scope This application note describes commands for the MIFARE Classic family of tags created by the NXP Corporation. These tags are used in contactless smart cards and proximity cards. 1.3 MIFARE Features The MIFARE Classic card is fundamentally a memory storage device, where the memory is divided into segments and blocks with simple security mechanisms for access control. They are ASIC-based and have limited computational power. Thanks to their reliability and low cost, these cards are widely used for electronic wallet, access control, corporate ID cards, transportation and stadium ticketing. 1.4 Accessing Memory Before any memory operation can be done, the MIFARE tag must be selected and authenticated. The possible memory operations for an addressed block depend on the key used and the access configuration as set up in each sector s trailing block. The following sections describe the memory structures of the MIFARE Classic 1k and Classic 4k.

5 U s i n g M I F A R E C l a s s i c T a g s P a g e MIFARE Classic 1k Memory Structure The MIFARE Classic 1K offers 1024 bytes of data storage, split into 16 sectors of 4 blocks, each containing 16 bytes of storage. The first block of memory is reserved for manufacturer data including the tag s UID. Each sector is protected by two different keys, called A and B, which are stored in the 4th block of each sector. Each sector key can be programmed to control the reading and writing operations within that sector. Figure 1-1 shows the memory structure of the MIFARE Classic 1k. Figure 1-1: MIFARE Classic 1k Memory Structure The addressing of the MIFARE s memory is done at the block level where each block address is sequential. For example block 2 of sector 1 is address 6. The access control for each sector is determined by the sector trailer which holds two keys as well as the access configuration bits. Additionally, access to the sector trailer itself is also determined by the access bits and therefore care must be taken to write the proper configuration during the personalization of new tags.

6 U s i n g M I F A R E C l a s s i c T a g s P a g e MIFARE Classic 4k Memory Structure MIFARE Classic 4K offers 4096 bytes split into forty sectors, of which 32 are same size as in the 1K with eight more that are quadruple size sectors. The following figure shows the structure of the MIFARE Classic 4k memory. Figure 1-2: MIFARE Classic 4k Memory Structure

7 U s i n g M I F A R E C l a s s i c T a g s P a g e MIFARE Classic Access Control Options The MIFARE Classic tags require key A while leaving key B as optional. If key B is not used for security it can be used for general data storage. The byte numbers for the sector trailer are shown in Figure 1-3. Figure 1-3: Sector Trailer Byte Numbering Within the access bits only 3 bytes (6,7, and 8) control the access for each block within that sector. The following figure illustrates how the individual access bits are structured. Figure 1-4: Access Control Bit Structure In Figure 1-4 the subscripts for each bit correspond to the block number within that sector to which that bit applies. In addition, each bits compliment is included for redundancy and security. Table 3 shows the access conditions for the sector trailer. NOTE MIFARE Classic Tags ship with key A set to 0xFFFFFFFFFFFF.

8 U s i n g M I F A R E C l a s s i c T a g s P a g e 8 Table 1-1: Sector Trailer Access Conditions MIFARE Classic tags are shipped in the transport configuration with C1 = 0, C2 = 0, and C3 = 0. In this configuration key A can be used to enable configuration of the access conditions. The access conditions for the data blocks are shown in the following table. [1] If key B may be read in the corresponding Sector Trailer it cannot serve for authentication (see grey marked lines in Table 4). As a consequences, if the reader authenticates any block of a sector which uses such access conditions for the Sector Trailer and using key B, the card will refuse any subsequent memory access after authentication. Table 1-2: Data Block Access Conditions

9 U s i n g M I F A R E C l a s s i c T a g s P a g e 9 For more information about value blocks, consult the tag s datasheet.

10 U s i n g M I F A R E C l a s s i c T a g s P a g e 10 2 Select Tag (0x0101) 2.1 Command Description This command queries a tag placed in the reader s field and returns the tag s TID (UID) in the response data. This command requires no flags to be set (except CRC if using binary communication). The returned TID is used for further communication to select a tag out of multiple tags which may be present in the reader s field. 2.2 Command Structure Flags This and all binary mode request commands require that the CRC flag be set. In addition, this command has the optional flags, RF and TID Fields This command requires the basic fields shown in in addition to the TID field if the TID flag is set. 2.3 Example 1 Selecting with Auto-detect Tag Type Request Start Message Length Flags Command Tag Type CRC F81A In this request the tag type field is set with the auto detect tag type (0x0000) and only the CRC flag set (0x0020). This causes the SkyeModule to respond with the tag type and TID of a tag in the reader field. NOTE More information about computing the CRC, tag types, commands, and flags can be found in the SkyeTek Protocol V3 Guide Response The response data from the tag depends on which MIFARE tag you are using however the general format for a MIFARE Classic 1k is illustrated below. Message Command Tag Start TID Length TID CRC Length Response Type C EEDAB 8EC2 The reader s response includes the requested command indicating a successful operation, the tag type number (0x0212) which corresponds to a MIFARE Classic 1k card, and the tag s TID which must be used in the next command in order to start a session with the tag.

11 U s i n g M I F A R E C l a s s i c T a g s P a g e Example 2 Starting a Tag Session using the TID This time repeat the select tag request while including the TID flag and RF flags as well as the TID and tag type fields Request Start Message Length Flags Command Tag Type TID Length TID CRC D EEDAB 2BCD The flag field is now 0x0068 due to the inclusion of the TID and RF Flags. The tag type has now been changed and the TID included, indicating the tag type and specific tag we would like to start a session with Response Message Command Start Data Length Data CRC Length Response F The response from the reader will include a session number in the data field which is to be included in subsequent commands in order to maintain secure communication with the tag.

12 U s i n g M I F A R E C l a s s i c T a g s P a g e 12 3 Authenticate Tag (0x0201) 3.1 Command Description This SkyeProtocol V3 command handles all of the authentication routines necessary to access your tags memory. 3.2 Command Structure Flags This command requires the session, RF, and CRC flags Fields The session number, address, and data fields are included in this request. NOTE MIFARE Classic Tags ship with key A set to 0xFFFFFFFFFFFF. 3.3 Example 1 Authenticating MIFARE Classic Tags Request The following examples shows the format of an authenticate tag command for the MIFARE Classic tag using the session number returned during the second tag select command. For this example we will authenticate to block 0 in sector 0 (address 0). The RF and session flags are set and so the TID does not need to be included. Message Tag Data Start Flags Cmd Session Address Data CRC Length Type Length C FFFFFFFFFFFF A6A2 NOTE The one-byte key value shown in bold is always 0x00 for key A and is any other value (0x01-0xFF) for key B. The next bytes define the key Response Start Message Length Command Response CRC The tag responds with the sent authenticate command (0x0201) if successful. Authentication between the tag and reader will allow access to all user blocks within that block s sector unless configured otherwise. Attempting to access a block address out of the valid range will return an error and the tag will have to be re-authenticated.

13 U s i n g M I F A R E C l a s s i c T a g s P a g e 13 4 Read Tag Data (0x0102) 4.1 Command Description This command is used to read blocks of data from a tag. MIFARE Classic cards require that an authenticated session be established before reading tag memory. 4.2 Command Structure Flags For this command we include the session, RF, and CRC flags. Note The TID flag is not required as long as the RF flag remains set Fields This command requires that a number of blocks be included in addition to an address. 4.3 Example 1 Reading MIFARE Tag Memory Request Now that the tag sector has been authenticated the tag will allow read and write operations to the tags memory blocks within that sector. The following examples illustrate reading data from the tag s memory. Number STX Message Length Flags Command Tag Type Session Address CRC Blocks D Response Message Command Data Start Data CRC Length Response Length EEDAB2C C11E A6A2 The 16 byte data block returned for block 1 is the manufacturer reserved block. The first 7 bytes of the data (shown in bold) are the tags UID while the remaining blocks are for manufacturer data.

14 U s i n g M I F A R E C l a s s i c T a g s P a g e Example 2 Reading different blocks within the authenticated sector Request To read the 2 nd block of data we issue the following command. Message Number STX Flags Command Tag Type Session Address CRC Length Blocks D AD Response Message Command STX Data Length Data CRC Length Response AF The second block of data is user data and is not defined on shipping. For our tag, the data should be zeros. 4.5 Example 3 Reading the sector trailer For the last example we ll look at the 4 th block of data (address 0x0003) which contains the sector trailer Request Message Number Start Flags Command Tag Type Session Address CRC Length Blocks D DF Response Sta Message Command Data Length Data CRC rt Length Response FF078069FFFFFFFFFFFF A6A2 The sector trailer contains keys A and B as well as the access control bits. Key A (underlined) always returns 0s and is never readable. Key B is shown shipped with 0xFFFFFFFFFFFF. The bits shown in bold are the access control bits. Writing an improper format to these bits will result in locking of the block, so take precaution to format this data as shown in section 1.7.

15 U s i n g M I F A R E C l a s s i c T a g s P a g e 15 5 Write Tag Data (0x0103) 5.1 Command Description This command is used to write data to a capable tag. Writing data to the MIFARE Classic tags can only be done with a tag in the authenticated state. See Section 3 for examples of authenticating a MIFARE Classic tag. 5.2 Command Structure Flags This command requires the RF, session, and CRC flags to be set Fields This command is similar to the read tag command however data length and data fields with the bits to be written must also be included. 5.3 Example 1 Writing a block of data In this example we will populate the second memory block with some example data Request Message Tag Number Data STX Flags Cmd Session Address Data CRC Length Type Blocks Length F 0C X 4AF1 [X = CAFEDEADBABEFADE ] The data X was chosen arbitrarily but must be 16 bytes long. The response data will include the write tag command indicating a success as shown below Response Start Message Length Data CRC You can now issue a read tag command again to see your data written to the block. That concludes this application note describing how to select, authenticate, and perform memory operations with MIFARE Classic tags.

16 U s i n g M I F A R E C l a s s i c T a g s P a g e 16 6 Revision History Revision Author Change Ryan Smith Initial release. Table 6-1: Revision History