3DES, AES, MD5 encryption and decryption Methods

---------- Des 8-bit key ---
/// <Summary>
/// String Encryption
/// </Summary>
/// <Param name = "strtext"> string to be encrypted </param>
/// <Param name = "strencrkey"> key </param>
/// <Returns> returns the encrypted string </returns>
Public static string desencrypt (string strtext, string strencrkey)
{
Byte [] bykey = NULL;
Byte [] IV = {0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef };
Try
{
Bykey = system. Text. encoding. utf8.getbytes (strencrkey. substring (0, strencrkey. Length ));
Descryptoserviceprovider des = new descryptoserviceprovider ();
Byte [] inputbytearray = encoding. utf8.getbytes (strtext );
Memorystream MS = new memorystream ();
Cryptostream cs = new cryptostream (MS, Des. createencryptor (bykey, IV), cryptostreammode. Write );
CS. Write (inputbytearray, 0, inputbytearray. Length );
CS. flushfinalblock ();
Return convert. tobase64string (Ms. toarray ());
}
Catch (system. Exception error)
{
Return "error:" + error. Message + "/R ";
}
}
/// <Summary>
/// String decryption
/// </Summary>
/// <Param name = "strtext"> string to be decrypted </param>
/// <Param name = "sdecrkey"> key </param>
/// <Returns> returns the decrypted string </returns>
Public static string desdecrypt (string strtext, string sdecrkey)
{
Byte [] bykey = NULL;
Byte [] IV = {0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef };
Byte [] inputbytearray = new byte [strtext. Length];
Try
{
Bykey = system. Text. encoding. utf8.getbytes (sdecrkey. substring (0, 8 ));
Descryptoserviceprovider des = new descryptoserviceprovider ();
Inputbytearray = convert. frombase64string (strtext );
Memorystream MS = new memorystream ();
Cryptostream cs = new cryptostream (MS, Des. createdecryptor (bykey, IV), cryptostreammode. Write );
CS. Write (inputbytearray, 0, inputbytearray. Length );
CS. flushfinalblock ();
System. Text. Encoding encoding = new system. Text. utf8encoding ();
Return encoding. getstring (Ms. toarray ());
}
Catch (system. Exception error)
{
Return "error:" + error. Message + "/R ";
}

}
------- 3DES 16-bit key ---------
/// <Summary>
/// 3DES encrypted string
/// </Summary>
/// <Param name = "a_strstring"> string to be encrypted </param>
/// <Param name = "a_strkey"> key </param>
/// <Returns> base64-encoded string </returns>
/// <Remarks> static method, which adopts the default ASCII encoding </remarks>
Public static string encryptdes16 (string a_strstring, string a_strkey)
{
Descryptoserviceprovider des = new descryptoserviceprovider ();

// Tripledescryptoserviceprovider des = new tripledescryptoserviceprovider ();
// Md5cryptoserviceprovider hashmd5 = new md5cryptoserviceprovider ();
Byte [] B = strtohexbyte (a_strkey );

Des. Key = B;
// Des. IV = B;
// Des. Key = B; // asciiencoding. ASCII. getbytes (a_strkey); // hashmd5.computehash (asciiencoding. ASCII. getbytes (a_strkey ));
Des. mode = ciphermode. ECB;
Des. Padding = paddingmode. pkcs7;

 

Icryptotransform desencrypt = des. createencryptor ();

Byte [] buffer = asciiencoding. utf8.getbytes (a_strstring );
Return convert. tobase64string (desencrypt. transformfinalblock (buffer, 0, buffer. Length ));
} // End Method

Private Static byte [] strtohexbyte (string hexstring)
{
Byte [] returnbytes = new byte [hexstring. Length/2];
For (INT I = 0; I <returnbytes. length; I ++)
Returnbytes [I] = convert. tobyte (hexstring. substring (I * 2, 2), 16 );
Return returnbytes;
}

/// <Summary>
/// 3DES decryption string
/// </Summary>
/// <Param name = "a_strstring"> string to be decrypted </param>
/// <Param name = "a_strkey"> key </param>
/// <Returns> decrypted string </returns>
/// <Exception CREF = ""> key error </exception>
/// <Remarks> static method, which adopts the default ASCII encoding </remarks>
Public static string decryptdes16 (string a_strstring, string a_strkey)
{
Descryptoserviceprovider des = new descryptoserviceprovider ();
Aescryptoserviceprovider AES = new aescryptoserviceprovider ();

Des. Key = strtohexbyte (a_strkey );
Des. mode = ciphermode. ECB;
Des. Padding = paddingmode. pkcs7;

Icryptotransform desdecrypt = des. createdecryptor ();

String result = "";
Try
{
Byte [] buffer = convert. frombase64string (a_strstring );
Result = asciiencoding. utf8.getstring (desdecrypt. transformfinalblock (buffer, 0, buffer. Length ));
}
Catch (exception E)
{

Throw (new exception ("invalid key or input string is not a valid base64 string", e ));
}

Return result;
}

---------- AES ----------
Public static byte [] aesendian (byte [] S1, byte [] key, byte [] IV, byte [] mainkey)
{

Aescryptoserviceprovider ACSP = new aescryptoserviceprovider ();
ACSP. mode = ciphermode. ECB;
ACSP. Padding = paddingmode. pkcs7;
// ACSP. Key = mainkey;
Memorystream mstream = new memorystream ();

Cryptostream cstream = new cryptostream (mstream, ACSP. createencryptor (Key, IV), cryptostreammode. Write );

Cstream. Write (S1, 0, s1.length );

Cstream. flushfinalblock ();

Byte [] outb1 = mstream. toarray ();

Cstream. Close ();

Mstream. Close ();

Return outb1;

}

Private Static byte [] _ key1 = {0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef, 0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef };

Public static byte [] aesdemo-( byte [] S2, byte [] key, byte [] IV, byte [] mainkey)
{

Aescryptoserviceprovider ACSP = new aescryptoserviceprovider ();
ACSP. mode = ciphermode. ECB;
ACSP. Padding = paddingmode. pkcs7;
// ACSP. Key = mainkey;
Memorystream mtream2 = new memorystream ();
Cryptostream destreame = new cryptostream (mtream2, ACSP. createdecryptor (Key, IV), cryptostreammode. Write );

Destreame. Write (S2, 0, s2.length );

Destreame. flushfinalblock ();

Byte [] outs2 = mtream2.toarray ();

Mtream2.close ();

Destreame. Close ();

Return outs2;

}

Call
Aescryptoserviceprovider ACSP = new aescryptoserviceprovider ();
Byte [] skey = encoding. Default. getbytes (key );
Byte [] SIV = {0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef, 0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef };
------------- MD5 --------------
Public static string MD5 (string STR, int code)
{
If (code = 16) // 16-bit MD5 encryption (take 32-bit encryption 9 ~ 25 characters)
{
Return System. Web. Security. formsauthentication. hashpasswordforstoringinconfigfile (STR, "MD5"). tolower (). substring (8, 16 );
}
Else // 32-bit encryption
{
Return System. Web. Security. formsauthentication. hashpasswordforstoringinconfigfile (STR, "MD5"). tolower ();
}
}
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