How decrypt a file that encypted in other windows xp os

Question

I am trying to find the indefinite integral of a polynomial, however neither my maths nor my coding is great. My code compiles but I believe I have the wrong formula:

Polynomial  Polynomial :: indefiniteIntegral() const
{
    Polynomial Result;
    Result.fDegree = fDegree + 1;
    for ( int i = fDegree; i > 0 ; i--){
        Result.fCoeffs[i] = pow(fCoeffs[i], (Result.fDegree)) / (Result.fDegree);
    }
    return Result;
}

Solution

See the Microsoft support article on decryption

Unless you saved the owner's public or private keys, it is possible that you will be unable to decrypt the files.

By far, the most frequent problem with EFS occurs when EFS encryption keys and/or recovery keys aren't archived. If keys aren't backed up, they cannot be replaced when lost. If keys cannot be used or replaced, data can be lost. If Windows is reinstalled (perhaps as the result of a disk crash) the keys are destroyed. If a user's profile is damaged, then keys are destroyed. In these, or in any other cases in which keys are damaged or lost and backup keys are unavailable, then encrypted files cannot be decrypted. The encryption keys are bound to the user account, and a new iteration of the operating system means new user accounts. A new user profile means new user keys. If keys are archived, or exported, they can be imported to a new account. If a revocation agent for the files exists, then that account can be used to recover the files. However, in many cases in which keys are destroyed, both user and revocation keys are absent and there is no backup, resulting in lost data.

Comments

[TypeIA]

Is fCoeffs a normal array (in which case it should be zero-indexed, while you appear to be 1-indexing it)?

[mvw]

\int a x^n dx = a/(n+1) x^{n+1} + C

[TypeIA]

Also you probably want to set Result.fCoeffs[i] based on this->fCoeffs[i - 1] (assuming lower array indices are lower-order coefficients). Conceptually the coefficients are shifting over. And I don't think you want pow() do you? Each coefficient of the integral is simply the original coefficient of the lower-order term divided by the order of the coefficient, right?

[Fred Larson]

I don't think the explicit cast is necessary, since i will be automatically promoted assuming fCoeffs is a container/array of float.

[celtschk]

Actually, it should be: Result.rCoeffs[0] = C because this is an indefinite integral. The C could be given as argument to indefiniteIntegral, unless fCoeffs is of a type that knows about the concept unspecified constant.

[duffymo]

This will be wildly inefficient for cases like p(x) = 1 + x^1000. Better to have a Monomial class and give Polynomial a collection of Monomials.

[mvw]

It depends on how the result is interpreted. I just guessed he keeps the arbitrary constant in mind.

[mvw]

Hey we have no clue if that is just homework or the seed of a computer algebra system. :-)