PrimesTest.java

package org.bouncycastle.math.test;

import java.math.BigInteger;
import java.security.SecureRandom;

import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;

import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.digests.SHA1Digest;
import org.bouncycastle.crypto.digests.SHA256Digest;
import org.bouncycastle.math.Primes;
import org.bouncycastle.math.Primes.MROutput;
import org.bouncycastle.math.Primes.STOutput;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.BigIntegers;

public class PrimesTest extends TestCase
{
    private static final int ITERATIONS = 10;
    private static final int PRIME_BITS = 256;
    private static final int PRIME_CERTAINTY = 100;

    private static final BigInteger TWO = BigInteger.valueOf(2);

    private static final SecureRandom R = new SecureRandom();

    public void testHasAnySmallFactors()
    {
        for (int iterations = 0; iterations < ITERATIONS; ++iterations)
        {
            BigInteger prime = randomPrime();
            assertFalse(Primes.hasAnySmallFactors(prime));

            // NOTE: Loop through ALL small values to be sure no small primes are missing
            for (int smallFactor = 2; smallFactor <= Primes.SMALL_FACTOR_LIMIT; ++smallFactor)
            {
                BigInteger nonPrimeWithSmallFactor = BigInteger.valueOf(smallFactor).multiply(prime);
                assertTrue(Primes.hasAnySmallFactors(nonPrimeWithSmallFactor));
            }
        }
    }

    public void testEnhancedMRProbablePrime()
    {
        int mrIterations = (PRIME_CERTAINTY + 1) / 2;
        for (int iterations = 0; iterations < ITERATIONS; ++iterations)
        {
            BigInteger prime = randomPrime();
            MROutput mr = Primes.enhancedMRProbablePrimeTest(prime, R, mrIterations);
            assertFalse(mr.isProvablyComposite());
            assertFalse(mr.isNotPrimePower());
            assertNull(mr.getFactor());

            BigInteger primePower = prime;
            for (int i = 0; i <= (iterations % 8); ++i)
            {
                primePower = primePower.multiply(prime);
            }

            MROutput mr2 = Primes.enhancedMRProbablePrimeTest(primePower, R, mrIterations);
            assertTrue(mr2.isProvablyComposite());
            assertFalse(mr2.isNotPrimePower());
            assertEquals(mr2.getFactor(), prime);

            BigInteger nonPrimePower = randomPrime().multiply(prime);
            MROutput mr3 = Primes.enhancedMRProbablePrimeTest(nonPrimePower, R, mrIterations);
            assertTrue(mr3.isProvablyComposite());
            assertTrue(mr3.isNotPrimePower());
            assertNull(mr.getFactor());
        }
    }

    public void testMRProbablePrime()
    {
        int mrIterations = (PRIME_CERTAINTY + 1) / 2;
        for (int iterations = 0; iterations < ITERATIONS; ++iterations)
        {
            BigInteger prime = randomPrime();
            assertTrue(Primes.isMRProbablePrime(prime, R, mrIterations));

            BigInteger nonPrime = randomPrime().multiply(prime);
            assertFalse(Primes.isMRProbablePrime(nonPrime, R, mrIterations));
        }
    }

    public void testMRProbablePrimeToBase()
    {
        int mrIterations = (PRIME_CERTAINTY + 1) / 2;
        for (int iterations = 0; iterations < ITERATIONS; ++iterations)
        {
            BigInteger prime = randomPrime();
            assertTrue(referenceIsMRProbablePrime(prime, mrIterations));

            BigInteger nonPrime = randomPrime().multiply(prime);
            assertFalse(referenceIsMRProbablePrime(nonPrime, mrIterations));
        }
    }

    public void testSTRandomPrime()
    {
        Digest[] digests = new Digest[]{ new SHA1Digest(), new SHA256Digest() };
        for (int digestIndex = 0; digestIndex < digests.length; ++digestIndex)
        {
            int coincidenceCount = 0;

            Digest digest = digests[digestIndex];
            for (int iterations = 0; iterations < ITERATIONS; ++iterations)
            {
                try
                {
                    byte[] inputSeed = new byte[16];
                    R.nextBytes(inputSeed);
    
                    STOutput st = Primes.generateSTRandomPrime(digest, PRIME_BITS, inputSeed);
                    assertTrue(isPrime(st.getPrime()));
    
                    STOutput st2 = Primes.generateSTRandomPrime(digest, PRIME_BITS, inputSeed);
                    assertEquals(st.getPrime(), st2.getPrime());
                    assertEquals(st.getPrimeGenCounter(), st2.getPrimeGenCounter());
                    assertTrue(Arrays.areEqual(st.getPrimeSeed(), st2.getPrimeSeed()));
    
                    for (int i = 0; i < inputSeed.length; ++i)
                    {
                        inputSeed[i] ^= 0xFF;
                    }
    
                    STOutput st3 = Primes.generateSTRandomPrime(digest, PRIME_BITS, inputSeed);
                    assertTrue(!st.getPrime().equals(st3.getPrime()));
                    assertFalse(Arrays.areEqual(st.getPrimeSeed(), st3.getPrimeSeed()));
    
                    if (st.getPrimeGenCounter() == st3.getPrimeGenCounter())
                    {
                        ++coincidenceCount;
                    }
                }
                catch (IllegalStateException e)
                {
                    if (e.getMessage().startsWith("Too many iterations"))
                    {
                        --iterations;
                        continue;
                    }

                    throw e;
                }
            }

            assertTrue(coincidenceCount * coincidenceCount < ITERATIONS);
        }
    }

    public static Test suite()
    {
        return new TestSuite(PrimesTest.class);
    }

    private static boolean referenceIsMRProbablePrime(BigInteger x, int numBases)
    {
        BigInteger xSubTwo = x.subtract(TWO);

        for (int i = 0; i < numBases; ++i)
        {
            BigInteger b = BigIntegers.createRandomInRange(TWO, xSubTwo, R);
            if (!Primes.isMRProbablePrimeToBase(x, b))
            {
                return false;
            }
        }

        return true;
    }

    private static boolean isPrime(BigInteger x)
    {
        return x.isProbablePrime(PRIME_CERTAINTY);
    }

    private static BigInteger randomPrime()
    {
        return new BigInteger(PRIME_BITS, PRIME_CERTAINTY, R);
    }
}