Decrypt string values from a column of a table in a query

[Sarazin73]

Hello,
i search to decrypt string values from a crypted column on a table imported as a query in my Power BI report.
The string is crypted in input with a XOR algorythm as follow :

String ToCrypt="";

for (int i=0; i< "sample_string".length();i++) {
           ToCrypt = ToCrypt + (char)("sample_string".charAt(i)^24); //(XOR 24)
}

How can i do in Power Query to decrypt in a new column the content of this crypted column for each row of my query ? (dataset). Thank you for yours ideas and comments

[Nolock]

Hi @Sarazin73,

do you also have the decryption algorithm in c-like code? If I had one, I'd develop a function in M for you.

And can you please post some examples for testing?

Thank you 🙂

[Sarazin73]

Hi,

Thanks for helphing me !
The algorythm used is the same to decryt than to encrypt. The initial outside script that crypt data as source is in java language. We have finally do tests with XOR 42 instead of XOR 24. Below, some samples with their corresponding encoding string.

Lundi : f_DNC

Mardi : gKXNC

Mercredi : gOXIXONC

Jeudi : `O_NC

Vendredi : |ODNXONC

Samedi : yKGONC

Dimanche : nCGKDIBO

[Nolock · Accepted solution]

Hi @Sarazin73,

I've written a custom function for you:

fnXorCrypt = (
    string as text, 
    xorValue as number
) as text =>
    // concat encrypted characters
    List.Accumulate(
        // get a list of chars
        Text.ToList(string),
        // initial string
        "",
        // accumulate last state and a new encrypted character
        (state, current) =>
            state 
            & 
            Character.FromNumber(
                Number.BitwiseXor(
                    Character.ToNumber(current), 
                    xorValue
                )
            )
    )

The usage:

EncodedString = fnXorCrypt("Lundi", 42)

A test:

[Sarazin73]

Hi NoLock,

thanks for your job. It's perfect !