1 files changed, 142 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/pqc/math/ntru/polynomial/DenseTernaryPolynomial.java b/core/src/main/java/org/spongycastle/pqc/math/ntru/polynomial/DenseTernaryPolynomial.java
new file mode 100644
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--- /dev/null
+++ b/core/src/main/java/org/spongycastle/pqc/math/ntru/polynomial/DenseTernaryPolynomial.java
@@ -0,0 +1,142 @@
+package org.spongycastle.pqc.math.ntru.polynomial;
+
+import java.security.SecureRandom;
+
+import org.spongycastle.pqc.math.ntru.util.Util;
+import org.spongycastle.util.Arrays;
+
+/**
+ * A <code>TernaryPolynomial</code> with a "high" number of nonzero coefficients.
+ */
+public class DenseTernaryPolynomial
+    extends IntegerPolynomial
+    implements TernaryPolynomial
+{
+
+    /**
+     * Constructs a new <code>DenseTernaryPolynomial</code> with <code>N</code> coefficients.
+     *
+     * @param N the number of coefficients
+     */
+    DenseTernaryPolynomial(int N)
+    {
+        super(N);
+        checkTernarity();
+    }
+
+    /**
+     * Constructs a <code>DenseTernaryPolynomial</code> from a <code>IntegerPolynomial</code>. The two polynomials are
+     * independent of each other.
+     *
+     * @param intPoly the original polynomial
+     */
+    public DenseTernaryPolynomial(IntegerPolynomial intPoly)
+    {
+        this(intPoly.coeffs);
+    }
+
+    /**
+     * Constructs a new <code>DenseTernaryPolynomial</code> with a given set of coefficients.
+     *
+     * @param coeffs the coefficients
+     */
+    public DenseTernaryPolynomial(int[] coeffs)
+    {
+        super(coeffs);
+        checkTernarity();
+    }
+
+    private void checkTernarity()
+    {
+        for (int i = 0; i != coeffs.length; i++)
+        {
+            int c = coeffs[i];
+            if (c < -1 || c > 1)
+            {
+                throw new IllegalStateException("Illegal value: " + c + ", must be one of {-1, 0, 1}");
+            }
+        }
+    }
+
+    /**
+     * Generates a random polynomial with <code>numOnes</code> coefficients equal to 1,
+     * <code>numNegOnes</code> coefficients equal to -1, and the rest equal to 0.
+     *
+     * @param N          number of coefficients
+     * @param numOnes    number of 1's
+     * @param numNegOnes number of -1's
+     */
+    public static DenseTernaryPolynomial generateRandom(int N, int numOnes, int numNegOnes, SecureRandom random)
+    {
+        int[] coeffs = Util.generateRandomTernary(N, numOnes, numNegOnes, random);
+        return new DenseTernaryPolynomial(coeffs);
+    }
+
+    /**
+     * Generates a polynomial with coefficients randomly selected from <code>{-1, 0, 1}</code>.
+     *
+     * @param N number of coefficients
+     */
+    public static DenseTernaryPolynomial generateRandom(int N, SecureRandom random)
+    {
+        DenseTernaryPolynomial poly = new DenseTernaryPolynomial(N);
+        for (int i = 0; i < N; i++)
+        {
+            poly.coeffs[i] = random.nextInt(3) - 1;
+        }
+        return poly;
+    }
+
+    public IntegerPolynomial mult(IntegerPolynomial poly2, int modulus)
+    {
+        // even on 32-bit systems, LongPolynomial5 multiplies faster than IntegerPolynomial
+        if (modulus == 2048)
+        {
+            IntegerPolynomial poly2Pos = (IntegerPolynomial)poly2.clone();
+            poly2Pos.modPositive(2048);
+            LongPolynomial5 poly5 = new LongPolynomial5(poly2Pos);
+            return poly5.mult(this).toIntegerPolynomial();
+        }
+        else
+        {
+            return super.mult(poly2, modulus);
+        }
+    }
+
+    public int[] getOnes()
+    {
+        int N = coeffs.length;
+        int[] ones = new int[N];
+        int onesIdx = 0;
+        for (int i = 0; i < N; i++)
+        {
+            int c = coeffs[i];
+            if (c == 1)
+            {
+                ones[onesIdx++] = i;
+            }
+        }
+        return Arrays.copyOf(ones, onesIdx);
+    }
+
+    public int[] getNegOnes()
+    {
+        int N = coeffs.length;
+        int[] negOnes = new int[N];
+        int negOnesIdx = 0;
+        for (int i = 0; i < N; i++)
+        {
+            int c = coeffs[i];
+            if (c == -1)
+            {
+                negOnes[negOnesIdx++] = i;
+            }
+        }
+        return Arrays.copyOf(negOnes, negOnesIdx);
+    }
+
+    public int size()
+    {
+        return coeffs.length;
+    }
+}