C# server side (encode) -> C++ client side (decode) ?

**Nicholas Paldino [.NET/C# MVP]** · Dec 24 '05, 07:45 AM

Re: C# server side (encode) -> C++ client side (decode) ?

J,

Sure you can. The classes in the System.Security .Cryptography namespace
use well established algorithms to encrypt/decrypt information. You just
have to use the same algorithms in your C++ code (which are supported, by
the way), along with the same key and iv values for encryption/decryption.

Hope this helps.

--
- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard. caspershouse.co m

<jtfaulk@eudora mail.com> wrote in message
news:1135116520 .216826.228810@ f14g2000cwb.goo glegroups.com.. .[color=blue]
>I need to encode some information on the server side using ASP.NET with
> C#; sending via HTTP to a client side application, that needs to be
> decoded in an MFC C++ application.
>
> I'm not sure if I can encode something using:
>
> C#: System.Security .Cryptography (to encode)
>
> and
>
> C++: wincrypt.h (to decode)
>
> Does anybody have any idea about this? Thank you in advance; it is
> greatly appreciated.
>
> J
>[/color]

**jtfaulk@eudoramail.com** · Jan 3 '06, 06:35 PM

Re: C# server side (encode) -> C++ client side (decode) ?

Ok, So my code is listed below. I'm not sure where to put the iv value
for the C++ portion:

I'm trying to encrypt a piece of information (a string of text from an
..INI file) on the server side (C# .net) and pass that information to
the client side app which has to decrypt it. I'm trying to use (in c#)
the System.Security .Cryptography and in c++ the wincrypt.h file. I'm
not sure if this is possible (although I believe it is); so I was
wondering if anybody had any ideas?

The C# Server Code:

// -----------------------------------------------------------
// ENCRYPT (C# SERVER SIDE)
// -----------------------------------------------------------
using System.Security .Cryptography;
private string Encrypt_Try2(st ring strKey, string strText)
{
PasswordDeriveB ytes cdk = new PasswordDeriveB ytes(strKey, null);

// generate an RC2 key
byte[] iv = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 };
byte[] key = cdk.CryptDerive Key("RC2", "MD5", 128, iv);
Console.WriteLi ne(key.Length * 8);

// setup an RC2 object to encrypt with the derived key
RC2CryptoServic eProvider rc2 = new RC2CryptoServic eProvider();
rc2.Key = key;
rc2.IV = new byte[] { 21, 22, 23, 24, 25, 26, 27, 28};

// now encrypt with it
byte[] plaintext = Encoding.UTF8.G etBytes(strText );
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms , rc2.CreateEncry ptor(),
CryptoStreamMod e.Write);

cs.Write(plaint ext, 0, plaintext.Lengt h);
cs.Close();
byte[] encrypted = ms.ToArray();

// Convert to Base64
string txtOut = Convert.ToBase6 4String(encrypt ed);

// THIS IS THE ENCRYPTED TEXT
return txtOut;
}

// -----------------------------------------------------------
// DECRYPT (FOR VERIFICATION - (C# SERVER SIDE))
// -----------------------------------------------------------
private string Decrypt_Try2(st ring strKey, string strText)
{
PasswordDeriveB ytes cdk = new PasswordDeriveB ytes(strKey, null);

// generate an RC2 key
byte[] iv = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 };
byte[] key = cdk.CryptDerive Key("RC2", "MD5", 128, iv);
Console.WriteLi ne(key.Length * 8);

// setup an RC2 object to encrypt with the derived key
RC2CryptoServic eProvider rc2 = new RC2CryptoServic eProvider();
rc2.Key = key;
rc2.IV = new byte[] { 21, 22, 23, 24, 25, 26, 27, 28};

// now encrypt with it
//byte[] plaintext = Encoding.UTF8.G etBytes(strText );
byte[] plaintext = Convert.FromBas e64String(strTe xt);
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms , rc2.CreateDecry ptor(),
CryptoStreamMod e.Write);

cs.Write(plaint ext, 0, plaintext.Lengt h);
cs.Close();
byte[] encrypted = ms.ToArray();

System.Text.Enc oding encoding = System.Text.Enc oding.UTF8;

// THIS IS THE DECRYPTED TEXT
return encoding.GetStr ing(encrypted);

//this.txtOut.Tex t = txtOut;
}

// -----------------------------------------------------------
// DECRYPT (C++ CLIENT SIDE)
// -----------------------------------------------------------

CString CJCrypt::Decryp t(char *key, char *txtOut)
{
char *szPassword = key;

CBase64Utils bu;
int iTxtOutLen = strlen(txtOut);
char *result = bu.Decode(txtOu t, &iTxtOutLen) ;

DWORD dwBufLen = 1+strlen(result );
HCRYPTPROV hCryptProv;
HCRYPTKEY hKey;
HCRYPTHASH hHashKey;
DWORD sts=0;
DWORD errc = 0;

sts = CryptAcquireCon text(&hCryptPro v, NULL, MS_ENHANCED_PRO V,
PROV_RSA_FULL, 0);
if(sts == 0) errc=GetLastErr or();

sts = CryptCreateHash (hCryptProv, CALG_MD5, 0, 0, &hHashKey);
if(sts == 0) errc=GetLastErr or();

sts = CryptHashData(h HashKey, (BYTE *)szPassword,
strlen(szPasswo rd), 0);
if(sts == 0) errc=GetLastErr or();

//sts = CryptDeriveKey( hCryptProv, CALG_DES, hHashKey, (56)<<16,
&hKey);

sts = CryptDeriveKey( hCryptProv, CALG_RC2, hHashKey, 128, &hKey);
//sts = CryptDeriveKey( hCryptProv, CALG_3DES, hHashKey, (168)<<16,
&hKey);
//sts = CryptDeriveKey( hCryptProv, CALG_RC4, hHashKey, (56)<<16,
&hKey);
if(sts == 0) errc=GetLastErr or();

DWORD dwCryptBuffLen = dwBufLen;
sts = CryptEncrypt(hK ey,0,TRUE,0,NUL L,&dwCryptBuffL en,0);
BYTE *bCryptoBuffer = new BYTE[dwCryptBuffLen];
memset(bCryptoB uffer,0,dwCrypt BuffLen);
memcpy(bCryptoB uffer,result,dw BufLen + 3);

sts = CryptDecrypt(hK ey, 0, TRUE,0,(BYTE *)result,
&dwCryptBuffLen );

if(sts == 0) errc=GetLastErr or();
// else do something with the dwBufLen bytes of encrypted data in
bCryptoBuffer

sts = CryptDestroyKey (hKey);
sts = CryptDestroyHas h(hHashKey);
sts = CryptReleaseCon text(hCryptProv , 0);

CString strOut;
strOut.Format(" %s", result);

return strOut;

}

// -----------------------------------------------------------
// ENCRYPT (FOR VERFICATION - (C++ CLIENT SIDE))
// -----------------------------------------------------------
CString CJCrypt::Encryp t(char *key, char *txtIn)
{
char *szPassword = key;

DWORD dwBufLen = 1+strlen(txtIn) ;
HCRYPTPROV hCryptProv;
HCRYPTKEY hKey;
HCRYPTHASH hHashKey;
DWORD sts=0;
DWORD errc = 0;

sts = CryptAcquireCon text(&hCryptPro v, NULL, MS_ENHANCED_PRO V,
PROV_RSA_FULL, 0);
if(sts == 0) errc=GetLastErr or();

sts = CryptCreateHash (hCryptProv, CALG_MD5, 0, 0, &hHashKey);
if(sts == 0) errc=GetLastErr or();

sts = CryptHashData(h HashKey, (BYTE *)szPassword,
strlen(szPasswo rd), 0);
if(sts == 0) errc=GetLastErr or();

//sts = CryptDeriveKey( hCryptProv, CALG_DES, hHashKey, (56)<<16,
&hKey);
sts = CryptDeriveKey( hCryptProv, CALG_RC2, hHashKey, 128, &hKey);
//sts = CryptDeriveKey( hCryptProv, CALG_3DES, hHashKey, (168)<<16,
&hKey);
//sts = CryptDeriveKey( hCryptProv, CALG_RC4, hHashKey, (56)<<16,
&hKey);
if(sts == 0) errc=GetLastErr or();

DWORD dwCryptBuffLen = dwBufLen;
sts = CryptEncrypt(hK ey,0,TRUE,0,NUL L,&dwCryptBuffL en,0);
BYTE *bCryptoBuffer = new BYTE[dwCryptBuffLen];
memset(bCryptoB uffer,0,dwCrypt BuffLen);
memcpy(bCryptoB uffer,txtIn,dwB ufLen);

sts = CryptEncrypt(hK ey, 0, TRUE, 0, bCryptoBuffer, &dwBufLen,
dwCryptBuffLen) ;

// Convert To Base64
CBase64Utils bu;
char *result = bu.Encode((char *)bCryptoBuffer , dwBufLen + 1);

if(sts == 0) errc=GetLastErr or();
// else do something with the dwBufLen bytes of encrypted data in
bCryptoBuffer

sts = CryptDestroyKey (hKey);
sts = CryptDestroyHas h(hHashKey);
sts = CryptReleaseCon text(hCryptProv , 0);

CString strOut;
strOut.Format(" %s", result);
return strOut;
}

Both the c# and c++ encrypt/decrypt work with them selves (i.e. I can
encrypt and decrypt things using only the c++ OR the C#, but I cannot
encrypt with C# and decrypt with C++). I'm not sure this is possible
and I just don't have the parameters set up correctly; or if they use
completely separate algorythms and will not work.

Does anybody have any idea?

Thank you very much

Nicholas Paldino [.NET/C# MVP] wrote:[color=blue]
> J,
>
> Sure you can. The classes in the System.Security .Cryptography namespace
> use well established algorithms to encrypt/decrypt information. You just
> have to use the same algorithms in your C++ code (which are supported, by
> the way), along with the same key and iv values for encryption/decryption.
>
> Hope this helps.
>
>
> --
> - Nicholas Paldino [.NET/C# MVP]
> - mvp@spam.guard. caspershouse.co m
>
> <jtfaulk@eudora mail.com> wrote in message
> news:1135116520 .216826.228810@ f14g2000cwb.goo glegroups.com.. .[color=green]
> >I need to encode some information on the server side using ASP.NET with
> > C#; sending via HTTP to a client side application, that needs to be
> > decoded in an MFC C++ application.
> >
> > I'm not sure if I can encode something using:
> >
> > C#: System.Security .Cryptography (to encode)
> >
> > and
> >
> > C++: wincrypt.h (to decode)
> >
> > Does anybody have any idea about this? Thank you in advance; it is
> > greatly appreciated.
> >
> > J
> >[/color][/color]

**Jon Skeet [C# MVP]** · Jan 3 '06, 07:35 PM

Re: C# server side (encode) -> C++ client side (decode) ?

<jtfaulk@eudora mail.com> wrote:[color=blue]
> Ok, So my code is listed below. I'm not sure where to put the iv value
> for the C++ portion:
>
> I'm trying to encrypt a piece of information (a string of text from an
> .INI file) on the server side (C# .net) and pass that information to
> the client side app which has to decrypt it. I'm trying to use (in c#)
> the System.Security .Cryptography and in c++ the wincrypt.h file. I'm
> not sure if this is possible (although I believe it is); so I was
> wondering if anybody had any ideas?[/color]

Having had a brief look at the C++ API, I believe you want to call
CryptSetKeyPara m, passing in KP_IV as the second parameter.

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

**jtfaulk@eudoramail.com** · Jan 6 '06, 12:45 AM

Re: C# server side (encode) -> C++ client side (decode) ?

Yeah, the problem is that I'm unable to generate the same key on both
c# and c++. This is the problem - does anybody have any ideas how to
solve this?

Jon wrote:[color=blue]
> <jtfaulk@eudora mail.com> wrote:[color=green]
> > Ok, So my code is listed below. I'm not sure where to put the iv value
> > for the C++ portion:
> >
> > I'm trying to encrypt a piece of information (a string of text from an
> > .INI file) on the server side (C# .net) and pass that information to
> > the client side app which has to decrypt it. I'm trying to use (in c#)
> > the System.Security .Cryptography and in c++ the wincrypt.h file. I'm
> > not sure if this is possible (although I believe it is); so I was
> > wondering if anybody had any ideas?[/color]
>
> Having had a brief look at the C++ API, I believe you want to call
> CryptSetKeyPara m, passing in KP_IV as the second parameter.
>
> --
> Jon Skeet - <skeet@pobox.co m>
> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
> If replying to the group, please do not mail me too[/color]

**Jon Skeet [C# MVP]** · Jan 6 '06, 07:45 AM

Re: C# server side (encode) -> C++ client side (decode) ?

<jtfaulk@eudora mail.com> wrote:[color=blue]
> Yeah, the problem is that I'm unable to generate the same key on both
> c# and c++. This is the problem - does anybody have any ideas how to
> solve this?[/color]

Hang on - you're unable to generate the same *key*, or the same IV? You
shouldn't be generating the key at all - that should be known
information.

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

**jtfaulk@eudoramail.com** · Jan 6 '06, 05:25 PM

Re: C# server side (encode) -> C++ client side (decode) ?

Ok, let say I assign the key (ie. hard code). That's fine; but I'm not
even sure how to do this. I simply cannot pass the same key to the c#
anc c++ encryption functions; therefore the output is not the same.

Do you have any ideas as to how to accomplish this? Let's say I want
to start (in c#) with the key:

byte[] testKey = {32, 44, 185, 98, 172, 89, 7, 91, 150, 75, 7, 21, 45,
35, 75, 112};

I have tried this and it works fine (it encrypts the original text).
But my problem is that now I cannot pass this same key to the
encryption process in c++.

How can I turn the above key into HCRYPTKEY and get the same results?

Thank you,

Jon wrote:[color=blue]
> <jtfaulk@eudora mail.com> wrote:[color=green]
> > Yeah, the problem is that I'm unable to generate the same key on both
> > c# and c++. This is the problem - does anybody have any ideas how to
> > solve this?[/color]
>
> Hang on - you're unable to generate the same *key*, or the same IV? You
> shouldn't be generating the key at all - that should be known
> information.
>
> --
> Jon Skeet - <skeet@pobox.co m>
> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
> If replying to the group, please do not mail me too[/color]

**Jon Skeet [C# MVP]** · Jan 6 '06, 05:45 PM

Re: C# server side (encode) -> C++ client side (decode) ?

<jtfaulk@eudora mail.com> wrote:[color=blue]
> Ok, let say I assign the key (ie. hard code). That's fine; but I'm not
> even sure how to do this. I simply cannot pass the same key to the c#
> anc c++ encryption functions; therefore the output is not the same.
>
> Do you have any ideas as to how to accomplish this? Let's say I want
> to start (in c#) with the key:
>
> byte[] testKey = {32, 44, 185, 98, 172, 89, 7, 91, 150, 75, 7, 21, 45,
> 35, 75, 112};
>
> I have tried this and it works fine (it encrypts the original text).
> But my problem is that now I cannot pass this same key to the
> encryption process in c++.
>
> How can I turn the above key into HCRYPTKEY and get the same results?[/color]

I'm afraid I don't know - I think you'd be best off asking that in a
Win32-specific group (or a Windows Security/Cryptography group).

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

C# server side (encode) -> C++ client side (decode) ?

C# server side (encode) -> C++ client side (decode) ?

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