Hi Sergey,

Well I guess the sys(2007) is out. I'm trying to do something that should be very simple, which is turning out to be very hard. If the long string below was 16 or less characters all I would do is val("123456789101112131415161718192021222324252627282930").
Then devide that by a number(15 in this case), which could be fully reversable.

Any ideas? Also I need to display the actual number without scientific notation.

Thanks, Stanley



>Hi,
>Does anyone know to calculate the reverse of a checksum that was generated with the SYS(2007) function? How are checksums calculated?
>
>Example: aa=val(sys(2007,"4848694856494948556965701264956495752505351565052")) / 15
>The calculated value of aa is 2840.9333
>
>Now, to authenticate, what do I do to calculate and get the value 15, when all I know is the 2840.9333 and the string of "4848694856494948556965701264956495752505351565052".

No it's not reversible. SYS(2007) always return 2 bytes integer regardless of the size of the string. Because of that the same checksum could be generated for different strings. There's an article at http://www.ciphersbyritter.com/ARTS/CRCMYST.HTM that discusses algorithm behind SYS(2007) in details.
For serious encripton take a look at http://fox.wikis.com/wc.dll?Wiki~FoxCrypto~VFP and Tap into Windows CryptoAPI Encryption file #9561.
Well I guess thats out.