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Thanks to Bing Shi
weidai11 · Nov 20, 2023 · eb383b8 · eb383b8
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Showing 2 changed files with 10 additions and 0 deletions.
diff --git a/gf2n.cpp b/gf2n.cpp
@@ -135,6 +135,9 @@ PolynomialMod2 PolynomialMod2::Monomial(size_t i)
 
 PolynomialMod2 PolynomialMod2::Trinomial(size_t t0, size_t t1, size_t t2)
 {
+	CRYPTOPP_ASSERT(t0 > t1);
+	CRYPTOPP_ASSERT(t1 > t2);
+
 	PolynomialMod2 r((word)0, t0+1);
 	r.SetBit(t0);
 	r.SetBit(t1);
@@ -144,6 +147,11 @@ PolynomialMod2 PolynomialMod2::Trinomial(size_t t0, size_t t1, size_t t2)
 
 PolynomialMod2 PolynomialMod2::Pentanomial(size_t t0, size_t t1, size_t t2, size_t t3, size_t t4)
 {
+	CRYPTOPP_ASSERT(t0 > t1);
+	CRYPTOPP_ASSERT(t1 > t2);
+	CRYPTOPP_ASSERT(t2 > t3);
+	CRYPTOPP_ASSERT(t3 > t4);
+
 	PolynomialMod2 r((word)0, t0+1);
 	r.SetBit(t0);
 	r.SetBit(t1);

diff --git a/gf2n.h b/gf2n.h
@@ -69,9 +69,11 @@ class CRYPTOPP_DLL PolynomialMod2
 		static PolynomialMod2 CRYPTOPP_API Monomial(size_t i);
 		/// \brief Provides x^t0 + x^t1 + x^t2
 		/// \return x^t0 + x^t1 + x^t2
+		/// \pre The coefficients should be provided in descending order. That is, <pre>t0 > t1 > t2<pre>.
 		static PolynomialMod2 CRYPTOPP_API Trinomial(size_t t0, size_t t1, size_t t2);
 		/// \brief Provides x^t0 + x^t1 + x^t2 + x^t3 + x^t4
 		/// \return x^t0 + x^t1 + x^t2 + x^t3 + x^t4
+		/// \pre The coefficients should be provided in descending order. That is, <pre>t0 > t1 > t2 > t3 > t4<pre>.
 		static PolynomialMod2 CRYPTOPP_API Pentanomial(size_t t0, size_t t1, size_t t2, size_t t3, size_t t4);
 		/// \brief Provides x^(n-1) + ... + x + 1
 		/// \return x^(n-1) + ... + x + 1