# CRC-8 & CRC-16

CRC - Cyclic Redundancy Check is widely used in data transition. According to `wikipedia.org`, A CRC-enabled device calculates a short, fixed-length binary sequence, known as the check value or CRC, for each block of data to be sent or stored and appends it to the data, forming a codeword.

`When a codeword is received or read, the device either compares its check value with one freshly calculated from the data block, or equivalently, performs a CRC on the whole codeword and compares the resulting check value with an expected residue constant.`\
`If the CRC values do not match, then the block contains a data error.`

It's really hard to calculate CRC value by hand, so we add CRC8 & CRC16 algorithm in [MTools](https://play.google.com/store/apps/details?id=tk.toolkeys.mtools).\
And this can really save your time to get the CRC values by one expression.\
\&#xNAN;***Notice: This is the feature from the full version.***

## Byte values

There exist 16 bytes on each block of the Mifare 1k card.\
And you can use `b0` `b1` `b2` ... `b14` `b15` for calculation.

## CRC-8

The value of the CRC-8 result is only 1 byte.\
Supported CRC8 algorithm in MTools.

| Algorithm      | Expression             | Value                                     |
| -------------- | ---------------------- | ----------------------------------------- |
| CRC-8          | crc8(**0,1,5,8**)      | CRC8 of HEX String of `b0` `b1` `b5` `b8` |
| CRC-8/CDMA2000 | crc8cdma2000(**0:14**) | CRC8-/CDMA2000 of `b0` to `b14`           |
| CRC-8/DARC     | crc8darc(**0:14**)     | idem                                      |
| CRC-8/DVB-S2   | crc8dvs2(**0:14**)     | idem                                      |
| CRC-8/EBU      | crc8eu(**0:14**)       | idem                                      |
| CRC-8/I-CODE   | crc8icode(**0:14**)    | idem                                      |
| CRC-8/ITU      | crc8itu(**0:14**)      | idem                                      |
| CRC-8/MAXIM    | crc8maxim(**0:14**)    | idem                                      |
| CRC-8/ROHC     | crc8rohc(**0:14**)     | idem                                      |
| CRC-8/WCDMA    | crc8wcdma(**0:14**)    | idem                                      |

## CRC-16

The value of CRC16 contains 2 bytes.\
To get these two separately, `0` or `1` need to be added after the expression.\
Supported CRC16 algorithm in MTools.

| Algorithm          | Expression 0           | Expression 1           | Xor Value             |
| ------------------ | ---------------------- | ---------------------- | --------------------- |
| CRC-16/CCITT-FALSE | crc16ccittfalse(0:14)0 | crc16ccittfalse(0:14)1 | crc16ccittfalse(0:14) |
| CRC-16/ARC         | crc16arc(0:14)0        | crc16arc(0:14)1        | crc16arc(0:14)        |
| CRC-16/AUG-CCITT   | crc16augccitt(0:14)0   | crc16augccitt(0:14)1   | crc16augccitt(0:14)   |
| CRC-16/BUYPASS     | crc16buypass(0:14)0    | crc16buypass(0:14)1    | crc16buypass(0:14)    |
| CRC-16/CDMA2000    | crc16cdma2000(0:14)0   | crc16cdma2000(0:14)1   | crc16cdma2000(0:14)   |
| CRC-16/DDS-110     | crc16dds110(0:14)0     | crc16dds110(0:14)1     | crc16dds110(0:14)     |
| CRC-16/DECT-R      | crc16dectr(0:14)0      | crc16dectr(0:14)1      | crc16dectr(0:14)      |
| CRC-16/DECT-X      | crc16dectx(0:14)0      | crc16dectx(0:14)1      | crc16dectx(0:14)      |
| CRC-16/DNP         | crc16dnp(0:14)0        | crc16dnp(0:14)1        | crc16dnp(0:14)        |
| CRC-16/EN-13757    | crc16en13757(0:14)0    | crc16en13757(0:14)1    | crc16en13757(0:14)    |
| CRC-16/GENIBUS     | crc16genibus(0:14)0    | crc16genibus(0:14)1    | crc16genibus(0:14)    |
| CRC-16/MAXIM       | crc16maxim(0:14)0      | crc16maxim(0:14)1      | crc16maxim(0:14)      |
| CRC-16/MCRF4XX     | crc16mcrf4xx(0:14)0    | crc16mcrf4xx(0:14)1    | crc16mcrf4xx(0:14)    |
| CRC-16/RIELLO      | crc16riello(0:14)0     | crc16riello(0:14)1     | crc16riello(0:14)     |
| CRC-16/T10-DIF     | crc16t10dif(0:14)0     | crc16t10dif(0:14)1     | crc16t10dif(0:14)     |
| CRC-16/TELEDISK    | crc16teledisk(0:14)0   | crc16teledisk(0:14)1   | crc16teledisk(0:14)   |
| CRC-16/TMS37157    | crc16tms37157(0:14)0   | crc16tms37157(0:14)1   | crc16tms37157(0:14)   |
| CRC-16/USB         | crc16usb(0:14)0        | crc16usb(0:14)1        | crc16usb(0:14)        |
| CRC-A              | crc16a(0:14)0          | crc16a(0:14)1          | crc16a(0:14)          |
| CRC-16/KERMIT      | crc16kermit(0:14)0     | crc16kermit(0:14)1     | crc16kermit(0:14)     |
| CRC-16/MODBUS      | crc16modbus(0:14)0     | crc16modbus(0:14)1     | crc16modbus(0:14)     |
| CRC-16/X-25        | crc16x25(0:14)0        | crc16x25(0:14)1        | crc16x25(0:14)        |
| CRC-16/XMODEM      | crc16xmodem(0:14)0     | crc16xmodem(0:14)1     | crc16xmodem(0:14)     |

## CRC-8 / CRC16 in Sniffer

The expression of the last byte `b15` is `CRC-8/MAXIM`, and the results are calculated correctly in a second. 

![](/files/-MbBngCneYcjPehEpWlX)


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