Function RecursiveSquare

src/cryptlib/integer.cpp:518–545

// A[N] --- number to be squared

void RecursiveSquare(word *R, word *T, const word *A, unsigned int N)
{
    assert(N && N%2==0);

    if (N==2)
        AtomicSquare(R, A[0], A[1]);
    else if (N==4)
    {
        AtomicSquare(R, A[0], A[1]);
        AtomicSquare(R+4, A[2], A[3]);
        AtomicMultiply(T, A[0], A[1], A[2], A[3]);
        word carry = Add(R+2, R+2, T, 4);
        carry += Add(R+2, R+2, T, 4);
        Increment(R+6, 2, carry);
    }
    else
    {
        const unsigned int N2 = N/2;

        RecursiveSquare(R0, T2, A0, N2);
        RecursiveSquare(R2, T2, A1, N2);
        RecursiveMultiply(T0, T2, A0, A1, N2);

        word carry = Add(R1, R1, T0, N);
        carry += Add(R1, R1, T0, N);
        Increment(R3, N2, carry);
    }
}

// R[N] - bottom half of A*B
// T[N] - temporary work space