sage: R.<x>=GF(2^8,'a')[]
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction( x^254 ) # the Boolean function Tr(x^254)
sage: BWhen defining a finite field of non-prime order, it is useful to give a name to the generator.
Likewise, when defining a polynomial ring, it is useful to give a name to the polynomial variable.
In the example, GF(2^8, 'a') returns the finite field with 28
elements, with a as the display name of its generator.
And R.<x> = K[] simultaneously defines R as a polynomial ring
over the field K, with a polynomial variable that displays as 'x',
and defines x as its generator, i.e., the polynomial variable.
So x^254 is the monic monomial of degree 254 in this polynomial ring.
For more, read the documentation or/and the source code for GF:
sage: GF?
sage: GF??and for PolynomialRing:
sage: PolynomialRing?
sage: PolynomialRing??Note that R.<x> = K[] is transformed by the Sage preparser into:
sage: preparse("R.<x> = K[]")
"R = K['x']; (x,) = R._first_ngens(1)"Asked: 6 years ago
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Last updated: May 08 '19
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