ideatest.java

MPI for java for Distributed Programming

        t1 = Z[k++];
        DK[j--] = Z[k++];
        DK[j--] = t1;
        t1 = inv(Z[k++]);
        t2 = -Z[k++] & 0xffff;
        t3 = -Z[k++] & 0xffff;
        DK[j--] = inv(Z[k++]);
        DK[j--] = t2;
        DK[j--] = t3;
        DK[j--] = t1;
    }

    t1 = Z[k++];
    DK[j--] = Z[k++];
    DK[j--] = t1;
    t1 = inv(Z[k++]);
    t2 = -Z[k++] & 0xffff;
    t3 = -Z[k++] & 0xffff;
    DK[j--] = inv(Z[k++]);
    DK[j--] = t3;
    DK[j--] = t2;
    DK[j--] = t1;
}

/*
* cipher_idea
*
* IDEA encryption/decryption algorithm. It processes plaintext in
* 64-bit blocks, one at a time, breaking the block into four 16-bit
* unsigned subblocks. It goes through eight rounds of processing
* using 6 new subkeys each time, plus four for last step. The source
* text is in array text1, the destination text goes into array text2
* The routine represents 16-bit subblocks and subkeys as type int so
* that they can be treated more easily as unsigned. Multiplication
* modulo 0x10001 interprets a zero sub-block as 0x10000; it must to
* fit in 16 bits.
*/

private void cipher_idea(byte [] text1, byte [] text2, int [] key)

{

int i1 = 0;                 // Index into first text array.
int i2 = 0;                 // Index into second text array.
int ik;                     // Index into key array.
int x1, x2, x3, x4, t1, t2; // Four "16-bit" blocks, two temps.
int r;                      // Eight rounds of processing.

for (int i = 0; i < text1.length; i += 8)
{

    ik = 0;                 // Restart key index.
    r = 8;                  // Eight rounds of processing.

    // Load eight plain1 bytes as four 16-bit "unsigned" integers.
    // Masking with 0xff prevents sign extension with cast to int.

    x1 = text1[i1++] & 0xff;          // Build 16-bit x1 from 2 bytes,
    x1 |= (text1[i1++] & 0xff) << 8;  // assuming low-order byte first.
    x2 = text1[i1++] & 0xff;
    x2 |= (text1[i1++] & 0xff) << 8;
    x3 = text1[i1++] & 0xff;
    x3 |= (text1[i1++] & 0xff) << 8;
    x4 = text1[i1++] & 0xff;
    x4 |= (text1[i1++] & 0xff) << 8;

    do {
        // 1) Multiply (modulo 0x10001), 1st text sub-block
        // with 1st key sub-block.

        x1 = (int) ((long) x1 * key[ik++] % 0x10001L & 0xffff);

        // 2) Add (modulo 0x10000), 2nd text sub-block
        // with 2nd key sub-block.

        x2 = x2 + key[ik++] & 0xffff;

        // 3) Add (modulo 0x10000), 3rd text sub-block
        // with 3rd key sub-block.

        x3 = x3 + key[ik++] & 0xffff;

        // 4) Multiply (modulo 0x10001), 4th text sub-block
        // with 4th key sub-block.

        x4 = (int) ((long) x4 * key[ik++] % 0x10001L & 0xffff);

        // 5) XOR results from steps 1 and 3.

        t2 = x1 ^ x3;

        // 6) XOR results from steps 2 and 4.
        // Included in step 8.

        // 7) Multiply (modulo 0x10001), result of step 5
        // with 5th key sub-block.

        t2 = (int) ((long) t2 * key[ik++] % 0x10001L & 0xffff);

        // 8) Add (modulo 0x10000), results of steps 6 and 7.

        t1 = t2 + (x2 ^ x4) & 0xffff;

        // 9) Multiply (modulo 0x10001), result of step 8
        // with 6th key sub-block.

        t1 = (int) ((long) t1 * key[ik++] % 0x10001L & 0xffff);

        // 10) Add (modulo 0x10000), results of steps 7 and 9.

        t2 = t1 + t2 & 0xffff;

        // 11) XOR results from steps 1 and 9.

        x1 ^= t1;

        // 14) XOR results from steps 4 and 10. (Out of order).

        x4 ^= t2;

        // 13) XOR results from steps 2 and 10. (Out of order).

        t2 ^= x2;

        // 12) XOR results from steps 3 and 9. (Out of order).

        x2 = x3 ^ t1;

        x3 = t2;        // Results of x2 and x3 now swapped.

    } while(--r != 0);  // Repeats seven more rounds.

    // Final output transform (4 steps).

    // 1) Multiply (modulo 0x10001), 1st text-block
    // with 1st key sub-block.

    x1 = (int) ((long) x1 * key[ik++] % 0x10001L & 0xffff);

    // 2) Add (modulo 0x10000), 2nd text sub-block
    // with 2nd key sub-block. It says x3, but that is to undo swap
    // of subblocks 2 and 3 in 8th processing round.

    x3 = x3 + key[ik++] & 0xffff;

    // 3) Add (modulo 0x10000), 3rd text sub-block
    // with 3rd key sub-block. It says x2, but that is to undo swap
    // of subblocks 2 and 3 in 8th processing round.

    x2 = x2 + key[ik++] & 0xffff;

    // 4) Multiply (modulo 0x10001), 4th text-block
    // with 4th key sub-block.

    x4 = (int) ((long) x4 * key[ik++] % 0x10001L & 0xffff);

    // Repackage from 16-bit sub-blocks to 8-bit byte array text2.

    text2[i2++] = (byte) x1;
    text2[i2++] = (byte) (x1 >>> 8);
    text2[i2++] = (byte) x3;                // x3 and x2 are switched
    text2[i2++] = (byte) (x3 >>> 8);        // only in name.
    text2[i2++] = (byte) x2;
    text2[i2++] = (byte) (x2 >>> 8);
    text2[i2++] = (byte) x4;
    text2[i2++] = (byte) (x4 >>> 8);

}   // End for loop.

}   // End routine.

/*
* mul
*
* Performs multiplication, modulo (2**16)+1. This code is structured
* on the assumption that untaken branches are cheaper than taken
* branches, and that the compiler doesn't schedule branches.
* Java: Must work with 32-bit int and one 64-bit long to keep
* 16-bit values and their products "unsigned." The routine assumes
* that both a and b could fit in 16 bits even though they come in
* as 32-bit ints. Lots of "& 0xFFFF" masks here to keep things 16-bit.
* Also, because the routine stores mod (2**16)+1 results in a 2**16
* space, the result is truncated to zero whenever the result would
* zero, be 2**16. And if one of the multiplicands is 0, the result
* is not zero, but (2**16) + 1 minus the other multiplicand (sort
* of an additive inverse mod 0x10001).

* NOTE: The java conversion of this routine works correctly, but
* is half the speed of using Java's modulus division function (%)
* on the multiplication with a 16-bit masking of the result--running
* in the Symantec Caje IDE. So it's not called for now; the test
* uses Java % instead.
*/

private int mul(int a, int b) throws ArithmeticException
{
    long p;             // Large enough to catch 16-bit multiply
                        // without hitting sign bit.
    if (a != 0)
    {
        if(b != 0)
        {
            p = (long) a * b;
            b = (int) p & 0xFFFF;       // Lower 16 bits.
            a = (int) p >>> 16;         // Upper 16 bits.

            return (b - a + (b < a ? 1 : 0) & 0xFFFF);
        }
        else
            return ((1 - a) & 0xFFFF);  // If b = 0, then same as
                                        // 0x10001 - a.
    }
    else                                // If a = 0, then return
        return((1 - b) & 0xFFFF);       // same as 0x10001 - b.
}

/*
* inv
*
* Compute multiplicative inverse of x, modulo (2**16)+1 using
* extended Euclid's GCD (greatest common divisor) algorithm.
* It is unrolled twice to avoid swapping the meaning of
* the registers. And some subtracts are changed to adds.
* Java: Though it uses signed 32-bit ints, the interpretation
* of the bits within is strictly unsigned 16-bit.
*/

private int inv(int x)
{
    int t0, t1;
    int q, y;

    if (x <= 1)             // Assumes positive x.
        return(x);          // 0 and 1 are self-inverse.

    t1 = 0x10001 / x;       // (2**16+1)/x; x is >= 2, so fits 16 bits.
    y = 0x10001 % x;
    if (y == 1)
        return((1 - t1) & 0xFFFF);

    t0 = 1;
    do {
        q = x / y;
        x = x % y;
        t0 += q * t1;
        if (x == 1) return(t0);
        q = y / x;
        y = y % x;
        t1 += q * t0;
    } while (y != 1);

    return((1 - t1) & 0xFFFF);
}

/*
* freeTestData
*
* Nulls arrays and forces garbage collection to free up memory.
*/

void freeTestData()
{
    plain1 = null;
    crypt1 = null;
    plain2 = null;
    p_plain1 = null;
    p_crypt1 = null;
    p_plain2 = null;
    userkey = null;
    Z = null;
    DK = null;

    System.gc();                // Force garbage collection.
}


}