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I have been playing around with my RPi2B (with Jessie), an adafruit breakout board and a RFID-RC522. I followed a guide to make it work, and it works like a charm Guide for adding RFID-RC522 to RPi2B

I have managed to change the information on the key, from all 00, to 1,2,3 etc, but I can't change the key used for authentication. The guide says that the key is a default key, only containing hexadecimal 0xFF, but I want to have my own key, especially if I use this to lock a door.

Is this possible?

I have included the code for the files I use.

Read.py for reading tags

#!/usr/bin/env python
# -*- coding: utf8 -*-

import RPi.GPIO as GPIO
import MFRC522
import signal

continue_reading = True

# Capture SIGINT for cleanup when the script is aborted
def end_read(signal,frame):
    global continue_reading
    print "Ctrl+C captured, ending read."
    continue_reading = False
    GPIO.cleanup()

# Hook the SIGINT
signal.signal(signal.SIGINT, end_read)

# Create an object of the class MFRC522
MIFAREReader = MFRC522.MFRC522()

# Welcome message
print "Welcome to the MFRC522 data read example"
print "Press Ctrl-C to stop."

# This loop keeps checking for chips. If one is near it will get the UID and authenticate
while continue_reading:

    # Scan for cards    
    (status,TagType) = MIFAREReader.MFRC522_Request(MIFAREReader.PICC_REQIDL)

    # If a card is found
    if status == MIFAREReader.MI_OK:
        print "Card detected"

    # Get the UID of the card
    (status,uid) = MIFAREReader.MFRC522_Anticoll()

    # If we have the UID, continue
    if status == MIFAREReader.MI_OK:

        # Print UID
        print "Card read UID: "+str(uid[0])+","+str(uid[1])+","+str(uid[2])+","+str(uid[3])

        if uid == [164,1,33,43,175]:
            print "WHITE CARD"

        # This is the default key for authentication
        key = [0xFF,0xFF,0xFF,0xFF,0xFF,0xFF]




        # Select the scanned tag
        MIFAREReader.MFRC522_SelectTag(uid)

        # Authenticate
        status = MIFAREReader.MFRC522_Auth(MIFAREReader.PICC_AUTHENT1A, 8, key, uid)

        # Check if authenticated
        if status == MIFAREReader.MI_OK:
            MIFAREReader.MFRC522_Read(8)
            MIFAREReader.MFRC522_StopCrypto1()
        else:
            print "Authentication error"

Write.py for writing tags

#!/usr/bin/env python
# -*- coding: utf8 -*-

import RPi.GPIO as GPIO
import MFRC522
import signal

continue_reading = True

# Capture SIGINT for cleanup when the script is aborted
def end_read(signal,frame):
    global continue_reading
    print "Ctrl+C captured, ending read."
    continue_reading = False
    GPIO.cleanup()

# Hook the SIGINT
signal.signal(signal.SIGINT, end_read)

# Create an object of the class MFRC522
MIFAREReader = MFRC522.MFRC522()

# This loop keeps checking for chips. If one is near it will get the UID and authenticate
while continue_reading:

    # Scan for cards    
    (status,TagType) = MIFAREReader.MFRC522_Request(MIFAREReader.PICC_REQIDL)

    # If a card is found
    if status == MIFAREReader.MI_OK:
        print "Card detected"

    # Get the UID of the card
    (status,uid) = MIFAREReader.MFRC522_Anticoll()

    # If we have the UID, continue
    if status == MIFAREReader.MI_OK:

        # Print UID
        print "Card read UID: "+str(uid[0])+","+str(uid[1])+","+str(uid[2])+","+str(uid[3])

        # This is the default key for authentication
        key = [0xFF,0xFF,0xFF,0xFF,0xFF,0xFF]

        # Select the scanned tag
        MIFAREReader.MFRC522_SelectTag(uid)

        # Authenticate
        status = MIFAREReader.MFRC522_Auth(MIFAREReader.PICC_AUTHENT1A, 8, key, uid)
        print "\n"

        # Check if authenticated
        if status == MIFAREReader.MI_OK:

            # Variable for the data to write
            data = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]

            # Fill the data with 0xFF
           # for x in range(0,16):
            #    data.append(0xFF)

            print "Sector 8 looked like this:"
            # Read block 8
            MIFAREReader.MFRC522_Read(8)
            print "\n"

            print "Sector 8 will now be filled with data in code:"
            # Write the data
            MIFAREReader.MFRC522_Write(8, data)
            print "\n"

            print "It now looks like this:"
            # Check to see if it was written
            MIFAREReader.MFRC522_Read(8)
            print "\n"

           # data = []
            # Fill the data with 0x00
            #for x in range(0,16):
             #   data.append(0x00)

            #print "Now we fill it with 0x00:"
            #MIFAREReader.MFRC522_Write(8, data)
            #print "\n"

            #print "It is now empty:"
            # Check to see if it was written
            #MIFAREReader.MFRC522_Read(8)
            #print "\n"

            # Stop
            MIFAREReader.MFRC522_StopCrypto1()

            # Make sure to stop reading for cards
            continue_reading = False
        else:
            print "Authentication error"

MFRC522.py containing the functions used in the two above

import RPi.GPIO as GPIO
import spi
import signal

class MFRC522:
  NRSTPD = 22

  MAX_LEN = 16

  PCD_IDLE       = 0x00
  PCD_AUTHENT    = 0x0E
  PCD_RECEIVE    = 0x08
  PCD_TRANSMIT   = 0x04
  PCD_TRANSCEIVE = 0x0C
  PCD_RESETPHASE = 0x0F
  PCD_CALCCRC    = 0x03

  PICC_REQIDL    = 0x26
  PICC_REQALL    = 0x52
  PICC_ANTICOLL  = 0x93
  PICC_SElECTTAG = 0x93
  PICC_AUTHENT1A = 0x60
  PICC_AUTHENT1B = 0x61
  PICC_READ      = 0x30
  PICC_WRITE     = 0xA0
  PICC_DECREMENT = 0xC0
  PICC_INCREMENT = 0xC1
  PICC_RESTORE   = 0xC2
  PICC_TRANSFER  = 0xB0
  PICC_HALT      = 0x50

  MI_OK       = 0
  MI_NOTAGERR = 1
  MI_ERR      = 2

  Reserved00     = 0x00
  CommandReg     = 0x01
  CommIEnReg     = 0x02
  DivlEnReg      = 0x03
  CommIrqReg     = 0x04
  DivIrqReg      = 0x05
  ErrorReg       = 0x06
  Status1Reg     = 0x07
  Status2Reg     = 0x08
  FIFODataReg    = 0x09
  FIFOLevelReg   = 0x0A
  WaterLevelReg  = 0x0B
  ControlReg     = 0x0C
  BitFramingReg  = 0x0D
  CollReg        = 0x0E
  Reserved01     = 0x0F

  Reserved10     = 0x10
  ModeReg        = 0x11
  TxModeReg      = 0x12
  RxModeReg      = 0x13
  TxControlReg   = 0x14
  TxAutoReg      = 0x15
  TxSelReg       = 0x16
  RxSelReg       = 0x17
  RxThresholdReg = 0x18
  DemodReg       = 0x19
  Reserved11     = 0x1A
  Reserved12     = 0x1B
  MifareReg      = 0x1C
  Reserved13     = 0x1D
  Reserved14     = 0x1E
  SerialSpeedReg = 0x1F

  Reserved20        = 0x20  
  CRCResultRegM     = 0x21
  CRCResultRegL     = 0x22
  Reserved21        = 0x23
  ModWidthReg       = 0x24
  Reserved22        = 0x25
  RFCfgReg          = 0x26
  GsNReg            = 0x27
  CWGsPReg          = 0x28
  ModGsPReg         = 0x29
  TModeReg          = 0x2A
  TPrescalerReg     = 0x2B
  TReloadRegH       = 0x2C
  TReloadRegL       = 0x2D
  TCounterValueRegH = 0x2E
  TCounterValueRegL = 0x2F

  Reserved30      = 0x30
  TestSel1Reg     = 0x31
  TestSel2Reg     = 0x32
  TestPinEnReg    = 0x33
  TestPinValueReg = 0x34
  TestBusReg      = 0x35
  AutoTestReg     = 0x36
  VersionReg      = 0x37
  AnalogTestReg   = 0x38
  TestDAC1Reg     = 0x39
  TestDAC2Reg     = 0x3A
  TestADCReg      = 0x3B
  Reserved31      = 0x3C
  Reserved32      = 0x3D
  Reserved33      = 0x3E
  Reserved34      = 0x3F

  serNum = []

  def __init__(self,spd=1000000):
    spi.openSPI(speed=spd)
    GPIO.setmode(GPIO.BOARD)
    GPIO.setup(22, GPIO.OUT)
    GPIO.output(self.NRSTPD, 1)
    self.MFRC522_Init()

  def MFRC522_Reset(self):
    self.Write_MFRC522(self.CommandReg, self.PCD_RESETPHASE)

  def Write_MFRC522(self,addr,val):
    spi.transfer(((addr<<1)&0x7E,val))

  def Read_MFRC522(self,addr):
    val = spi.transfer((((addr<<1)&0x7E) | 0x80,0))
    return val[1]

  def SetBitMask(self, reg, mask):
    tmp = self.Read_MFRC522(reg)
    self.Write_MFRC522(reg, tmp | mask)

  def ClearBitMask(self, reg, mask):
    tmp = self.Read_MFRC522(reg);
    self.Write_MFRC522(reg, tmp & (~mask))

  def AntennaOn(self):
    temp = self.Read_MFRC522(self.TxControlReg)
    if(~(temp & 0x03)):
      self.SetBitMask(self.TxControlReg, 0x03)

  def AntennaOff(self):
    self.ClearBitMask(self.TxControlReg, 0x03)

  def MFRC522_ToCard(self,command,sendData):
    backData = []
    backLen = 0
    status = self.MI_ERR
    irqEn = 0x00
    waitIRq = 0x00
    lastBits = None
    n = 0
    i = 0

    if command == self.PCD_AUTHENT:
      irqEn = 0x12
      waitIRq = 0x10
    if command == self.PCD_TRANSCEIVE:
      irqEn = 0x77
      waitIRq = 0x30

    self.Write_MFRC522(self.CommIEnReg, irqEn|0x80)
    self.ClearBitMask(self.CommIrqReg, 0x80)
    self.SetBitMask(self.FIFOLevelReg, 0x80)

    self.Write_MFRC522(self.CommandReg, self.PCD_IDLE);  

    while(i<len(sendData)):
      self.Write_MFRC522(self.FIFODataReg, sendData[i])
      i = i+1

    self.Write_MFRC522(self.CommandReg, command)

    if command == self.PCD_TRANSCEIVE:
      self.SetBitMask(self.BitFramingReg, 0x80)

    i = 2000
    while True:
      n = self.Read_MFRC522(self.CommIrqReg)
      i = i - 1
      if ~((i!=0) and ~(n&0x01) and ~(n&waitIRq)):
        break

    self.ClearBitMask(self.BitFramingReg, 0x80)

    if i != 0:
      if (self.Read_MFRC522(self.ErrorReg) & 0x1B)==0x00:
        status = self.MI_OK

        if n & irqEn & 0x01:
          status = self.MI_NOTAGERR

        if command == self.PCD_TRANSCEIVE:
          n = self.Read_MFRC522(self.FIFOLevelReg)
          lastBits = self.Read_MFRC522(self.ControlReg) & 0x07
          if lastBits != 0:
            backLen = (n-1)*8 + lastBits
          else:
            backLen = n*8

          if n == 0:
            n = 1
          if n > self.MAX_LEN:
            n = self.MAX_LEN

          i = 0
          while i<n:
            backData.append(self.Read_MFRC522(self.FIFODataReg))
            i = i + 1;
      else:
        status = self.MI_ERR

    return (status,backData,backLen)


  def MFRC522_Request(self, reqMode):
    status = None
    backBits = None
    TagType = []

    self.Write_MFRC522(self.BitFramingReg, 0x07)

    TagType.append(reqMode);
    (status,backData,backBits) = self.MFRC522_ToCard(self.PCD_TRANSCEIVE, TagType)

    if ((status != self.MI_OK) | (backBits != 0x10)):
      status = self.MI_ERR

    return (status,backBits)


  def MFRC522_Anticoll(self):
    backData = []
    serNumCheck = 0

    serNum = []

    self.Write_MFRC522(self.BitFramingReg, 0x00)

    serNum.append(self.PICC_ANTICOLL)
    serNum.append(0x20)

    (status,backData,backBits) = self.MFRC522_ToCard(self.PCD_TRANSCEIVE,serNum)

    if(status == self.MI_OK):
      i = 0
      if len(backData)==5:
        while i<4:
          serNumCheck = serNumCheck ^ backData[i]
          i = i + 1
        if serNumCheck != backData[i]:
          status = self.MI_ERR
      else:
        status = self.MI_ERR

    return (status,backData)

  def CalulateCRC(self, pIndata):
    self.ClearBitMask(self.DivIrqReg, 0x04)
    self.SetBitMask(self.FIFOLevelReg, 0x80);
    i = 0
    while i<len(pIndata):
      self.Write_MFRC522(self.FIFODataReg, pIndata[i])
      i = i + 1
    self.Write_MFRC522(self.CommandReg, self.PCD_CALCCRC)
    i = 0xFF
    while True:
      n = self.Read_MFRC522(self.DivIrqReg)
      i = i - 1
      if not ((i != 0) and not (n&0x04)):
        break
    pOutData = []
    pOutData.append(self.Read_MFRC522(self.CRCResultRegL))
    pOutData.append(self.Read_MFRC522(self.CRCResultRegM))
    return pOutData

  def MFRC522_SelectTag(self, serNum):
    backData = []
    buf = []
    buf.append(self.PICC_SElECTTAG)
    buf.append(0x70)
    i = 0
    while i<5:
      buf.append(serNum[i])
      i = i + 1
    pOut = self.CalulateCRC(buf)
    buf.append(pOut[0])
    buf.append(pOut[1])
    (status, backData, backLen) = self.MFRC522_ToCard(self.PCD_TRANSCEIVE, buf)

    if (status == self.MI_OK) and (backLen == 0x18):
      print("Size: " + str(backData[0]))
      return  backData[0]
    else:
      return 0

  def MFRC522_Auth(self, authMode, BlockAddr, Sectorkey, serNum):
    buff = []
    buff.append(authMode)
    buff.append(BlockAddr)
    i = 0
    while(i < len(Sectorkey)):
      buff.append(Sectorkey[i])
      i = i + 1
    i = 0
    while(i < len(serNum)):
      buff.append(serNum[i])
      i = i +1
    (status, backData, backLen) = self.MFRC522_ToCard(self.PCD_AUTHENT,buff)
    if not(status == self.MI_OK):
      print("AUTH ERROR!!")
    if not (self.Read_MFRC522(self.Status2Reg) & 0x08) != 0:
      print("AUTH ERROR(status2reg & 0x08) != 0")

    return status

  def MFRC522_Read(self, blockAddr):
    recvData = []
    recvData.append(self.PICC_READ)
    recvData.append(blockAddr)
    pOut = self.CalulateCRC(recvData)
    recvData.append(pOut[0])
    recvData.append(pOut[1])
    (status, backData, backLen) = self.MFRC522_ToCard(self.PCD_TRANSCEIVE, recvData)
    if not(status == self.MI_OK):
      print("Error while reading!")

    print("Got data size: "+str(backLen))
    i = 0
    if len(backData) == 16:
      print("Sector "+str(blockAddr)+" "+str(backData))

  def MFRC522_Write(self, blockAddr, writeData):
    buff = []
    buff.append(self.PICC_WRITE)
    buff.append(blockAddr)
    crc = self.CalulateCRC(buff)
    buff.append(crc[0])
    buff.append(crc[1])
    (status, backData, backLen) = self.MFRC522_ToCard(self.PCD_TRANSCEIVE, buff)
    if not(status == self.MI_OK) or not(backLen == 4) or not((backData[0] & 0x0F) == 0x0A):
      status = self.MI_ERR

    print(str(backLen)+" backdata &0x0F == 0x0A "+str(backData[0]&0x0F))
    if status == self.MI_OK:
        i = 0
        buf = []
        while i < 16:
          buf.append(writeData[i])
          i = i + 1
        crc = self.CalulateCRC(buf)
        buf.append(crc[0])
        buf.append(crc[1])
        (status, backData, backLen) = self.MFRC522_ToCard(self.PCD_TRANSCEIVE,buf)
        if not(status == self.MI_OK) or not(backLen == 4) or not((backData[0] & 0x0F) == 0x0A):
          print("Error while writing")
        if status == self.MI_OK:
          print("Data writen")


  def MFRC522_Init(self):
    GPIO.output(self.NRSTPD, 1)

    self.MFRC522_Reset();


    self.Write_MFRC522(self.TModeReg, 0x8D)
    self.Write_MFRC522(self.TPrescalerReg, 0x3E)
    self.Write_MFRC522(self.TReloadRegL, 30)
    self.Write_MFRC522(self.TReloadRegH, 0)

    self.Write_MFRC522(self.TxAutoReg, 0x40)
    self.Write_MFRC522(self.ModeReg, 0x3D)
    self.AntennaOn()

  def GPIO_CLEEN(self):
    GPIO.cleanup() 
1

RFID tags contain 2 parts: a unique identifier, and a data payload. While the data payload is always read/write, the unique identifier (often called UID or serial number) is not always read/write. Post the specific make and model of your key, we can look it up.

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