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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.7. Note: this package includes the IDEA and NTRU encryption algorithms.

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package org.bouncycastle.pqc.math.linearalgebra;

import java.security.SecureRandom;

public class RandUtils
{
    static int nextInt(SecureRandom rand, int n)
    {

        if ((n & -n) == n)  // i.e., n is a power of 2
        {
            return (int)((n * (long)(rand.nextInt() >>> 1)) >> 31);
        }

        int bits, value;
        do
        {
            bits = rand.nextInt() >>> 1;
            value = bits % n;
        }
        while (bits - value + (n - 1) < 0);

        return value;
    }
}