Cyclic Redundancy Check (CRC)

1. Cyclic Redundancy Check
(CRC)
Appasami G
NITT

2. Cyclic Redundancy Check (CRC)
• A cyclic redundancy check (CRC) is an error-detecting code commonly
used in digital networks and storage devices to detect accidental
changes to raw data.
• Blocks of data entering these systems get a short check value
attached, based on the remainder of a polynomial division of their
contents.
• On retrieval, the calculation is repeated and, in the event the check
values do not match, corrective action can be taken against data
corruption.
• CRCs can be used for error correction (Analysis Technique using
bitfilters).

3. Cyclic Redundancy Check (CRC)
• CRC is based on division in the ring of polynomials over the finite field
GF(2) (the integers modulo 2), that is, the set of polynomials where
each coefficient is either zero or one.
• Cyclic redundancy checking is a method of checking for errors in data
that has been transmitted on a communications link.
• A sending device applies a 16- or 32-bit polynomial to a block of data
that is to be transmitted and appends the resulting cyclic redundancy
code (CRC) to the block.
• The receiving end applies the same polynomial to the data and
compares its result with the result appended by the sender.
• If they agree, the data has been received successfully. If not, the
sender can be notified to resend the block of data.

4. Example: Write the CRC code with C(7,4).

5. Example: Draw the CRC encoder and decoder

8. Thank you