C / C++ / MFC

Re: RC4 encryption problems... *updated*

22-Jul-02 14:10

Sorry for msg below, i forgot to disable HTML.. Anyways, read on...

This function uses RC4's algorithm, but its not working properly. It works on small strings, but not large binarys. I cant find the bug in it.. Its tickin me off! Do you see anything wrong?

Usage;

strcpy(buffer, "This is my test string");
EncryptRC4(buffer, strlen(buffer), "secret", 6);

// buffer is then over-written with the new encrypted string.
// to un-encrypt, just call it again.

EncryptRC4(buffer, strlen(buffer), "secret", 6);

// buffer now holds orginal message.
// using strlen here isnt smart, because NULL character may be generated somewhere in the string buffer, but it fits the demo.

Function;

void EncryptRC4(char *sBuffer, int iBufferLen, char *sKey, int iKeyLen)
{
unsigned char sBox[256], k;
int iOffset, i = 0, j = 0;

for (i = 0; i < 256; i++)
sBox[i] = i;

for (i = 0; i < 256; i++) {
j = (j + sBox[i] + sKey[i % iKeyLen]) % 256;
k = sBox[i];
sBox[i] = sBox[j];
sBox[j] = k;
}

i = 0; j = 0;

for (iOffset = 0; iOffset < iBufferLen; iOffset++) {
i = (i + 1) % 256;
j = (j + sBox[i]) % 256;
k = sBox[i];
sBox[i] = sBox[j];
sBox[j] = k;
sBuffer[iOffset] = sBuffer[iOffset] ^ sBox[(sBox[i] + sBox[j]) % 256];
}
}

Anonymous22-Jul-02 18:53

RC4 encryption problems...

22-Jul-02 18:53

Ok, I'm an idiot! That function works perfectly! I just realized after 2 days of debugging, that the function is perfectly fine... it was that I was using the 'get' member function instead of the 'read' member function of the fstream class.... So i was reading the file in wrong... so it was encrypting the wrong data... LOL ... Blah! Basically the obove function works perfectly for anyone that would like to use it.

Anonymous22-Jul-02 14:09

Winsock Error 10038 while FTPing

22-Jul-02 14:09

Ok, I simplified it down to just a function instead of a class. This function uses RC4's algorithm, but its not working properly. It works on small strings, but not large binarys. I cant find the bug in it.. Its tickin me off! Do you see anything wrong?

Usage;

strcpy(buffer, "This is my test string");
EncryptRC4(buffer, strlen(buffer), "secret", 6);

// buffer is then over-written with the new encrypted string.
// to un-encrypt, just call it again.

EncryptRC4(buffer, strlen(buffer), "secret", 6);

// buffer now holds orginal message.
// using strlen here isnt smart, because NULL character may be generated somewhere in the string buffer, but it fits the demo.

Function;

void EncryptRC4(char *sBuffer, int iBufferLen, char *sKey, int iKeyLen)
{
unsigned char sBox[256], k;
int iOffset, i = 0, j = 0;

for (i = 0; i < 256; i++)
sBox[i] = i;

for (i = 0; i < 256; i++) {
j = (j + sBox[i] + sKey[i % iKeyLen]) % 256;
k = sBox[i];
sBox[i] = sBox[j];
sBox[j] = k;
}

i = 0; j = 0;

for (iOffset = 0; iOffset < iBufferLen; iOffset++) {
i = (i + 1) % 256;
j = (j + sBox[i]) % 256;
k = sBox[i];
sBox[i] = sBox[j];
sBox[j] = k;
sBuffer[iOffset] = sBuffer[iOffset] ^ sBox[(sBox[i] + sBox[j]) % 256];
}
}

Anonymous22-Jul-02 11:54

22-Jul-02 11:54

well ppl!
i have got a real trouble here ,
i am trying to send the 'APPE' (Append) to a FTP server
the other commands like REST or TYPE go well but the data storing or retriving commands give error
WINSOCK error 10038 - socket operaton on non-socket
what to do about it
how to remove it so that i be able to send some data !

PLZZZZZZZZZZ help me

Need Help with IPC in C

Klumsy22-Jul-02 11:51

Klumsy

22-Jul-02 11:51

Hello,

i am somehow new to C programming.
i did a plugin (DLL) written in C and now i need to write an EXE that has to send events to that DLL. I read some articles and i think the best way is to do that with shared memory. There are some articles around with code samples but all use MFC which is not supported in C Frown | :(

Can someone pls provide with me with information how to do that in C? Maybe there is a library that may makes things a bit easier?

Thanks for you help

Alexandru Savescu22-Jul-02 23:07

Alexandru Savescu

22-Jul-02 23:07

Why do you need to send events to that DLL. Why not load it from your exe directly?

Best regards,
Alexandru Savescu

jan larsen23-Jul-02 0:23

jan larsen

23-Jul-02 0:23

Your question is a little blurred and i'm not quite sure on what your'e trying to accomplish.
But if you want to share data sections in a DLL then you could do something like this:

#pragma data_seg(".sdata")
int iSharedVar = 0;
#pragma data_seg()

Remember to modify your .DEF file:

SECTIONS
.sdata   READ WRITE SHARED

The recommended approach though is using file mappings, this is by the way the underlying technology for the implementation of eg. pipes on Win32. Look up CreateFileMapping and MapViewOfFile in MSDN for details.

"It could have been worse, it could have been ME!" -Rincewind

Anonymous23-Jul-02 0:57

23-Jul-02 0:57

thanks for for reply Smile | :)

okay, sorry i try to make it a bit clearer.
The plugin (DLL) is for a program I use (it's not written by me). The DLL is not for EXE i want to write. The EXE is to control the other program (which loads the DLL) via the plugin. Therefore I need IPC because it is 2 different processes.

"Application.exe"
loads DLL <------ "control.exe" sends events to DLL

i hope this helps Wink | ;)

How to convert CString to char*?

jan larsen23-Jul-02 1:22

jan larsen

23-Jul-02 1:22

If i understand you correct:

You have written a plugin P, the DLL.
The plugin corresponds to a plugin standard known to the application X that loads P.
You want to send a message to P that will somehow be detected by X.

In that case any of the methods i described are valid, by the way, remember to use some sort of synchronization when using mapped files or shared sections. You could take a look at CreateMutex in MSDN.

Hmm..., I guess i didn't tell you how to set up the loop that checks for the shared data to change, but why spoil all the fun. Big Grin | :-D

But here is a hint: Loop could be set up in DLLMain(), remember to Sleep() sometimes so you won't get exhausted...

You could probably also use som Win32 Event functionality, but I haven't actually got any experience in this, but looking up CreateEvent in MSDN seems like a good idea (just did that and it seems to be what your'e looking for).

"It could have been worse, it could have been ME!" -Rincewind

nachilau22-Jul-02 11:06

nachilau

22-Jul-02 11:06

Hello,

Can anyone tell me how to convert CString to char*?

Thanks!

C^hris L^osinger22-Jul-02 11:09

C^hris L^osinger

22-Jul-02 11:09

did you try (char *)csMyCString ?

-c

To explain Donald Knuth's relevance to computing is like explaining Paul's relevance to the Catholic Church. He isn't God, he isn't the Son of God, but he was sent by God to explain God to the masses.
/. #3848917

Fractals!

Navin22-Jul-02 11:20

Navin

22-Jul-02 11:20

It depends - do you want a constant char *? Then doing as Chris said works fine (and usually happens automatically.)

If you want a char * that's not constant, try CString::GetBuffer (and CString::ReleaseBuffer when you're done with the char *.)

Good ol' strcpy to a char array also works. Smile | :)

Even if you win the rat race, you're still a rat.

Dave Bryant22-Jul-02 11:20

Dave Bryant

22-Jul-02 11:20

If you only need a constant string, you can use the implicit LPCTSTR operator of CString, which under ANSI builds will give you a const char*. If you need a non-constant string, then you can use the GetBuffer() method to get direct access to the underlying buffer, and then ReleaseBuffer() when you have finished with it.

Dave

paulb22-Jul-02 15:04

paulb

22-Jul-02 15:04

You can also do...

(LPTSTR) (LPCTSTR) strYourString

it's a bit dangerous though but can be useful when you need a LPTSTR and know it won't ever be modified.

GBlank22-Jul-02 20:45

GBlank

22-Jul-02 20:45

Yeah:

1)
CString csTemp = "bla bla";
char *szResult;
szResult = new char[csTemp.GetLength() + 1];
strcpy(szResult,csTemp);

or

csTemp.GetBuffer(0); //This returns char*

vikramlinux22-Jul-02 21:08

vikramlinux

22-Jul-02 21:08

in MSDN there is one example given
Example

The following example demonstrates the use of CString::operator LPCSTR.

// If the prototype of a function is known to the compiler,
// the LPCTSTR cast operator may be invoked implicitly

CString strSports(_T("Hockey is Best!"));
TCHAR sz[1024];

lstrcpy(sz, strSports);

// If the prototype isn't known, or is a va_arg prototype,
// you must invoke the cast operator explicitly. For example,
// the va_arg part of a call to sprintf() needs the cast:

sprintf(sz, "I think that %s!\n", (LPCTSTR) strSports);

// while the format parameter is known to be an LPCTSTR and
// therefore doesn't need the cast:

sprintf(sz, strSports);

// Note that some situations are ambiguous. This line will
// put the address of the strSports object to stdout:

cout << strSports;

// while this line will put the content of the string out:

cout << (LPCTSTR) strSports;