Search results
Results from the WOW.Com Content Network
Computing the remainder then consists of subtracting multiples of the generator polynomial (). This is just like decimal long division, but even simpler because the only possible multiples at each step are 0 and 1, and the subtractions borrow "from infinity" instead of reducing the upper digits. Because we do not care about the quotient, there ...
Since the only invertible element is 1, division is the identity function. Elements of GF( p n ) may be represented as polynomials of degree strictly less than n over GF( p ). Operations are then performed modulo m(x) where m(x) is an irreducible polynomial of degree n over GF( p ), for instance using polynomial long division .
Classical modular multiplication reduces the double-width product ab using division by N and keeping only the remainder. This division requires quotient digit estimation and correction. The Montgomery form, in contrast, depends on a constant R > N which is coprime to N, and the only division necessary in Montgomery multiplication is division by R.
A convenient block size would be 8 bits, although this is not required. Similarly, a convenient modulus would be 255, although, again, others could be chosen. So, the simple checksum is computed by adding together all the 8-bit bytes of the message, dividing by 255 and keeping only the remainder.
Long division is the standard algorithm used for pen-and-paper division of multi-digit numbers expressed in decimal notation. It shifts gradually from the left to the right end of the dividend, subtracting the largest possible multiple of the divisor (at the digit level) at each stage; the multiples then become the digits of the quotient, and the final difference is then the remainder.
In algebra, synthetic division is a method for manually performing Euclidean division of polynomials, with less writing and fewer calculations than long division. It is mostly taught for division by linear monic polynomials (known as Ruffini's rule ), but the method can be generalized to division by any polynomial .
A Euclidean division (division with remainder) can be performed within the same time bounds. The cost of a polynomial greatest common divisor between two polynomials of degree at most n can be taken as O ( n 2 ) operations in F q using classical methods, or as O ( n log 2 ( n ) log(log( n )) ) operations in F q using fast methods.
An erroneous message can be detected in a straightforward way through polynomial division by the generator polynomial resulting in a non-zero remainder. Assuming that the code word is free of errors, a systematic code can be decoded simply by stripping away the m {\displaystyle m} checksum digits.