String Encoding in C Sharp

[Anti_Evil]

سلام مهندس،
آقا میتونی کدی ... لینکی .. چیزی در مورد string encoding در net. بهم بدی ؟

[Vahid_Nasiri]

به صورت پیش فرض انکدینگ آن utf-8 است. مشکل شما الان چیست؟

[Anti_Evil]

آخ آقا شرمنده من اشتباه نوشتم :oops:
منظورم string encryption هستش، برای کد کردن string به منظور استفاده در قطعات امنیتی در برنامه ها ...

[Farhad.B.S]

http://msdn.microsoft.com/asp.net/using/understanding/security/default.aspx?pull=/library/en-us/dnnetsec/html/cryptosimplified.asp

[Vahid_Nasiri]

:wink:
--------
یک سری مقاله کریپتوگرافی البته در مورد VB.NET است ولی اصول یکی است چون فضاهای نام یکی است :
http://www.devx.com/security/Article/7019/0/page/1

برای استفاده از DES :



using System;
using System.IO;
using System.Text;
using System.Security;
using System.Security.Cryptography;
using System.Web.Services;

namespace FE_SymmetricNamespace
{
public class FE_Symmetric
{
static private Byte[] m_Key = new Byte[8];
static private Byte[] m_IV = new Byte[8];

//////////////////////////
//Function to encrypt data
public string EncryptData(String strKey, String strData)
{
string strResult; //Return Result

//1. String Length cannot exceed 90Kb. Otherwise, buffer will overflow. See point 3 for reasons
if (strData.Length > 92160)
{
strResult="Error. Data String too large. Keep within 90Kb.";
return strResult;
}

//2. Generate the Keys
if (!InitKey(strKey))
{
strResult="Error. Fail to generate key for encryption";
return strResult;
}

//3. Prepare the String
// The first 5 character of the string is formatted to store the actual length of the data.
// This is the simplest way to remember to original length of the data, without resorting to complicated computations.
// If anyone figure a good way to 'remember' the original length to facilite the decryption without having to use additional function parameters, pls let me know.
strData = String.Format("{0,5:00000}"+strData, strData.Length);


//4. Encrypt the Data
byte[] rbData = new byte[strData.Length];
ASCIIEncoding aEnc = new ASCIIEncoding();
aEnc.GetBytes(strData, 0, strData.Length, rbData, 0);

DESCryptoServiceProvider descsp = new DESCryptoServiceProvider();

ICryptoTransform desEncrypt = descsp.CreateEncryptor(m_Key, m_IV);


//5. Perpare the streams:
// mOut is the output stream.
// mStream is the input stream.
// cs is the transformation stream.
MemoryStream mStream = new MemoryStream(rbData);
CryptoStream cs = new CryptoStream(mStream, desEncrypt, CryptoStreamMode.Read);
MemoryStream mOut = new MemoryStream();

//6. Start performing the encryption
int bytesRead;
byte[] output = new byte[1024];
do
{
bytesRead = cs.Read(output,0,1024);
if (bytesRead != 0)
mOut.Write(output,0,bytesRead);
} while (bytesRead > 0);

//7. Returns the encrypted result after it is base64 encoded
// In this case, the actual result is converted to base64 so that it can be transported over the HTTP protocol without deformation.
if (mOut.Length == 0)
strResult = "";
else
strResult = Convert.ToBase64String(mOut.GetBuffer(), 0, (int)mOut.Length);

return strResult;
}

//////////////////////////
//Function to decrypt data
public string DecryptData(String strKey, String strData)
{
string strResult;

//1. Generate the Key used for decrypting
if (!InitKey(strKey))
{
strResult="Error. Fail to generate key for decryption";
return strResult;
}

//2. Initialize the service provider
int nReturn = 0;
DESCryptoServiceProvider descsp = new DESCryptoServiceProvider();
ICryptoTransform desDecrypt = descsp.CreateDecryptor(m_Key, m_IV);

//3. Prepare the streams:
// mOut is the output stream.
// cs is the transformation stream.
MemoryStream mOut = new MemoryStream();
CryptoStream cs = new CryptoStream(mOut, desDecrypt, CryptoStreamMode.Write);

//4. Remember to revert the base64 encoding into a byte array to restore the original encrypted data stream
byte[] bPlain = new byte[strData.Length];
try
{
bPlain = Convert.FromBase64CharArray(strData.ToCharArray(), 0, strData.Length);
}
catch (Exception)
{
strResult = "Error. Input Data is not base64 encoded.";
return strResult;
}

long lRead = 0;
long lTotal = strData.Length;

try
{
//5. Perform the actual decryption
while (lTotal >= lRead)
{
cs.Write(bPlain,0,(int)bPlain.Length);
//descsp.BlockSize=64
lRead = mOut.Length + Convert.ToUInt32(((bPlain.Length / descsp.BlockSize) * descsp.BlockSize));
};

ASCIIEncoding aEnc = new ASCIIEncoding();
strResult = aEnc.GetString(mOut.GetBuffer(), 0, (int)mOut.Length);

//6. Trim the string to return only the meaningful data
// Remember that in the encrypt function, the first 5 character holds the length of the actual data
// This is the simplest way to remember to original length of the data, without resorting to complicated computations.
String strLen = strResult.Substring(0,5);
int nLen = Convert.ToInt32(strLen);
strResult = strResult.Substring(5, nLen);
nReturn = (int)mOut.Length;

return strResult;
}
catch (Exception)
{
strResult = "Error. Decryption Failed. Possibly due to incorrect Key or corrputed data";
return strResult;
}
}

/////////////////////////////////////////////////////////////
//Private function to generate the keys into member variables
static private bool InitKey(String strKey)
{
try
{
// Convert Key to byte array
byte[] bp = new byte[strKey.Length];
ASCIIEncoding aEnc = new ASCIIEncoding();
aEnc.GetBytes(strKey, 0, strKey.Length, bp, 0);

//Hash the key using SHA1
SHA1CryptoServiceProvider sha = new SHA1CryptoServiceProvider();
byte[] bpHash = sha.ComputeHash(bp);

int i;
// use the low 64-bits for the key value
for (i=0; i<8; i++)
m_Key[i] = bpHash[i];

for (i=8; i<16; i++)
m_IV[i-8] = bpHash[i];

return true;
}
catch (Exception)
{
//Error Performing Operations
return false;
}
}
}
}

----------

البته اگر کمی صبر کنید بخش کریپتوگرافی سایت را باید گرم تر کرد :idea:

[Anti_Evil]

ایول !!! مرسی آقا فرهاد ... همونه که میخواستم :wink:

[Anti_Evil]

آقا وحید ممنون ! خیلی توپه !
برای من همین کافیه مهندس :wink:
دستت طلا !