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In mathematics and computer programming, exponentiating by squaring is a general method for fast computation of large positive integer powers of a number, or more generally of an element of a semigroup, like a polynomial or a square matrix. Some variants are commonly referred to as square-and-multiply algorithms or binary exponentiation.
Here, the order of the generator, | g |, is the number of non-zero elements of the field. In the case of GF(2 8) this is 2 8 − 1 = 255. That is to say, for the Rijndael example: (x + 1) 255 = 1. So this can be performed with two look up tables and an integer subtract. Using this idea for exponentiation also derives benefit:
In mathematics, a generating function is a representation of an infinite sequence of numbers as the coefficients of a formal power series.Generating functions are often expressed in closed form (rather than as a series), by some expression involving operations on the formal series.
Modular exponentiation can be done using exponentiation by squaring by initializing the initial product to the Montgomery representation of 1, that is, to R mod N, and by replacing the multiply and square steps by Montgomery multiplies. Performing these operations requires knowing at least N′ and R 2 mod N.
The runtime bottleneck of Shor's algorithm is quantum modular exponentiation, which is by far slower than the quantum Fourier transform and classical pre-/post-processing. There are several approaches to constructing and optimizing circuits for modular exponentiation.
Modular exponentiation is the remainder when an integer b (the base) is raised to the power e (the exponent), and divided by a positive integer m (the modulus); that is, c = b e mod m. From the definition of division, it follows that 0 ≤ c < m .
Formally, is a generator of some group (typically the multiplicative group of a finite field or an elliptic curve group) and and are randomly chosen integers. For example, in the Diffie–Hellman key exchange, an eavesdropper observes g x {\displaystyle g^{x}} and g y {\displaystyle g^{y}} exchanged as part of the protocol, and the two parties ...
Again, the group sizes to be chosen depend on the exact details of how fast signals propagate within logic gates and from one logic gate to another. For very large numbers (hundreds or even thousands of bits), lookahead-carry logic does not become any more complex, because more layers of supergroups and supersupergroups can be added as necessary.