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pre-reduction multiplication result in binary field

asked 2017-09-03 22:44:52 -0600

The following will do multiplication in a finite field:

X = Integer(0x009D73616F35F4AB1407D73562C10F);
Y = Integer(0x00A52830277958EE84D1315ED31886);

F.<x> = GF(2)[];
p = x^113 + x^9 + 1;
BF = GF(2^113, 'x', modulus=p);

X_bf = BF._cache.fetch_int(X);
Y_bf = BF._cache.fetch_int(Y);

temp = Y * X; temp

The problem with this is that the result you get back has had the reduction step already ran. I'd like to see the multiplication result pre-reduction.

Any ideas?

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answered 2017-09-04 07:39:52 -0600

B r u n o gravatar image

updated 2017-09-04 07:44:48 -0600

If you want to see the polynomial result before reduction, you can use the method polynomial which gives you the polynomial representing the element of your binary field, as an element of the polynomial ring. That is:

sage: X_poly = X_bf.polynomial()
sage: Y_poly = Y_bf.polynomial()
sage: X_poly * Y_poly
x^222 + x^220 + x^219 + x^218 + x^217 + x^216 + x^215 + x^214 + x^213 + x^211 + x^205 + x^204 + x^203 + x^202 + x^200 + x^199 + x^198 + x^197 + x^191 + x^188 + x^186 + x^185 + x^182 + x^179 + x^178 + x^177 + x^176 + x^175 + x^172 + x^171 + x^170 + x^169 + x^163 + x^160 + x^159 + x^154 + x^152 + x^151 + x^149 + x^146 + x^143 + x^140 + x^136 + x^132 + x^131 + x^128 + x^127 + x^126 + x^125 + x^124 + x^123 + x^120 + x^119 + x^116 + x^115 + x^113 + x^111 + x^110 + x^109 + x^106 + x^105 + x^103 + x^101 + x^97 + x^96 + x^94 + x^88 + x^85 + x^83 + x^82 + x^80 + x^75 + x^70 + x^68 + x^67 + x^66 + x^65 + x^64 + x^61 + x^58 + x^57 + x^55 + x^54 + x^46 + x^44 + x^43 + x^41 + x^35 + x^34 + x^31 + x^30 + x^27 + x^24 + x^23 + x^20 + x^18 + x^17 + x^16 + x^15 + x^11 + x^8 + x^7 + x^5 + x

And if you want the result as an integer:

sage: sum(2^i for i in _.exponents()) # _ represents the latest result
10100206405814666335316365818931450998837311752455571104712025934242
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Asked: 2017-09-03 22:44:52 -0600

Seen: 48 times

Last updated: Sep 04