gost3410parametersgenerator.java

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                }
            }
        }
        return y[0].longValue();
    }

    //Procedure B
    private void procedure_B(int x0, int c, BigInteger[] pq)
    {
        //Verify and perform condition: 0<x<2^16; 0<c<2^16; c - odd.
        while(x0<0 || x0>65536)
        {
            x0 = init_random.nextInt()/32768;
        }

        while((c<0 || c>65536) || (c/2==0))
        {
            c = init_random.nextInt()/32768 + 1;
        }

        BigInteger [] qp = new BigInteger[2];
        BigInteger q = null, Q = null, p = null;
        BigInteger C = new BigInteger(Integer.toString(c));
        BigInteger constA16 = new BigInteger("19381");

        //step1
        x0 = procedure_A(x0, c, qp, 256);
        q = qp[0];

        //step2
        x0 = procedure_A(x0, c, qp, 512);
        Q = qp[0];

        BigInteger[] y = new BigInteger[65];
        y[0] = new BigInteger(Integer.toString(x0));

        int tp = 1024;

 step3: for(;;)
        {
            //step 3
            for (int j=0; j<64; j++)
            {
                y[j+1] = (y[j].multiply(constA16).add(C)).mod(TWO.pow(16));
            }

            //step 4
            BigInteger Y = new BigInteger("0");
 
            for (int j=0; j<64; j++)
            {
                Y = Y.add(y[j].multiply(TWO.pow(16*j)));
            }

            y[0] = y[64]; //step 5

            //step 6
            BigInteger N = TWO.pow(tp-1).divide(q.multiply(Q)).
                               add((TWO.pow(tp-1).multiply(Y)).
                                   divide(q.multiply(Q).multiply(TWO.pow(1024))));

            if (N.mod(TWO).compareTo(ONE)==0)
            {
                N = N.add(ONE);
            }

            int k = 0; //step 7

     step8: for(;;)
            {
                //step 11
                p = q.multiply(Q).multiply(N.add(BigInteger.valueOf(k))).add(ONE);

                if (p.compareTo(TWO.pow(tp))==1)
                {
                    continue step3; //step 9
                }

                //step10
                if ((TWO.modPow(q.multiply(Q).multiply(N.add(BigInteger.valueOf(k))),p).compareTo(ONE)==0) &&
                    (TWO.modPow(q.multiply(N.add(BigInteger.valueOf(k))),p).compareTo(ONE)!=0))
                {
                    pq[0] = p;
                    pq[1] = q;
                    return;
                }
                else
                {
                    k += 2;
                    continue step8;
                }
            }
        }
    }

    //Procedure B'
    private void procedure_Bb(long x0, long c, BigInteger[] pq)
    {
        //Verify and perform condition: 0<x<2^32; 0<c<2^32; c - odd.
        while(x0<0 || x0>4294967296L)
        {
            x0 = init_random.nextInt()*2;
        }

        while((c<0 || c>4294967296L) || (c/2==0))
        {
            c = init_random.nextInt()*2+1;
        }

        BigInteger [] qp = new BigInteger[2];
        BigInteger q = null, Q = null, p = null;
        BigInteger C = new BigInteger(Long.toString(c));
        BigInteger constA32 = new BigInteger("97781173");

        //step1
        x0 = procedure_Aa(x0, c, qp, 256);
        q = qp[0];

        //step2
        x0 = procedure_Aa(x0, c, qp, 512);
        Q = qp[0];

        BigInteger[] y = new BigInteger[33];
        y[0] = new BigInteger(Long.toString(x0));

        int tp = 1024;

 step3: for(;;)
        {
            //step 3
            for (int j=0; j<32; j++)
            {
                y[j+1] = (y[j].multiply(constA32).add(C)).mod(TWO.pow(32));
            }

            //step 4
            BigInteger Y = new BigInteger("0");
            for (int j=0; j<32; j++)
            {
                Y = Y.add(y[j].multiply(TWO.pow(32*j)));
            }

            y[0] = y[32]; //step 5

            //step 6
            BigInteger N = TWO.pow(tp-1).divide(q.multiply(Q)).
                               add((TWO.pow(tp-1).multiply(Y)).
                                   divide(q.multiply(Q).multiply(TWO.pow(1024))));

            if (N.mod(TWO).compareTo(ONE)==0)
            {
                N = N.add(ONE);
            }

            int k = 0; //step 7

     step8: for(;;)
            {
                //step 11
                p = q.multiply(Q).multiply(N.add(BigInteger.valueOf(k))).add(ONE);

                if (p.compareTo(TWO.pow(tp))==1)
                {
                    continue step3; //step 9
                }

                //step10
                if ((TWO.modPow(q.multiply(Q).multiply(N.add(BigInteger.valueOf(k))),p).compareTo(ONE)==0) &&
                    (TWO.modPow(q.multiply(N.add(BigInteger.valueOf(k))),p).compareTo(ONE)!=0))
                {
                    pq[0] = p;
                    pq[1] = q;
                    return;
                }
                else
                {
                    k += 2;
                    continue step8;
                }
            }
        }
    }


    /**
     * Procedure C
     * procedure generates the a value from the given p,q,
     * returning the a value.
     */
    private BigInteger procedure_C(BigInteger p, BigInteger q)
    {
        BigInteger pSub1 = p.subtract(ONE);
        BigInteger pSub1DivQ = pSub1.divide(q);
        int length = p.bitLength();

        for(;;)
        {
            BigInteger d = new BigInteger(length, init_random);

            // 1 < d < p-1
            if (d.compareTo(ONE) > 0 && d.compareTo(pSub1) < 0)
            {
                BigInteger a = d.modPow(pSub1DivQ, p);

                if (a.compareTo(ONE) != 0)
                {
                    return a;
                }
            }
        }
    }

    /**
     * which generates the p , q and a values from the given parameters,
     * returning the GOST3410Parameters object.
     */
    public GOST3410Parameters generateParameters()
    {
        BigInteger [] pq = new BigInteger[2];
        BigInteger    q = null, p = null, a = null;

        int  x0, c;
        long  x0L, cL;

        if (typeproc==1)
        {
            x0 = init_random.nextInt();
            c  = init_random.nextInt();

            switch(size)
            {
            case 512:  
                procedure_A(x0, c, pq, 512); 
                break;
            case 1024: 
                procedure_B(x0, c, pq); 
                break;
            default: 
                throw new IllegalArgumentException("Ooops! key size 512 or 1024 bit.");
            }
            p = pq[0];  q = pq[1];
            a = procedure_C(p, q);
            //System.out.println("p:"+p.toString(16)+"\n"+"q:"+q.toString(16)+"\n"+"a:"+a.toString(16));
            //System.out.println("p:"+p+"\n"+"q:"+q+"\n"+"a:"+a);
            return new GOST3410Parameters(p, q, a, new GOST3410ValidationParameters(x0, c));
        }
        else
        {
            x0L = init_random.nextLong();
            cL  = init_random.nextLong();

            switch(size)
            {
            case 512:  
                procedure_Aa(x0L, cL, pq, 512); 
                break;
            case 1024: 
                procedure_Bb(x0L, cL, pq); 
                break;
            default: 
                throw new IllegalStateException("Ooops! key size 512 or 1024 bit.");
            }
            p = pq[0];  q = pq[1];
            a = procedure_C(p, q);
            //System.out.println("p:"+p.toString(16)+"\n"+"q:"+q.toString(16)+"\n"+"a:"+a.toString(16));
            //System.out.println("p:"+p+"\n"+"q:"+q+"\n"+"a:"+a);
            return new GOST3410Parameters(p, q, a, new GOST3410ValidationParameters(x0L, cL));
        }
    }
}