Encrypt and Decrypt a String in c#

Question

_{Thursday, July 12, 2012 11:30 AM}

Hi,

How to encrypt and decrypt a given string using any possible algorithm. I need the code in C#. Can someone pls help ?

Thanks

All replies (21)

_{Thursday, July 12, 2012 12:51 PM ✅Answered | 5 votes}

Here is an encrption using popular RSA Alogorithm.

public string EncryptString( string inputString, int dwKeySize,                              string xmlString ){        RSACryptoServiceProvider rsaCryptoServiceProvider =                                   new RSACryptoServiceProvider( dwKeySize );    rsaCryptoServiceProvider.FromXmlString( xmlString );    int keySize = dwKeySize / 8;    byte[] bytes = Encoding.UTF32.GetBytes( inputString );    RSACryptoServiceProvider here         int maxLength = keySize - 42;    int dataLength = bytes.Length;    int iterations = dataLength / maxLength;    StringBuilder stringBuilder = new StringBuilder();    for( int i = 0; i <= iterations; i++ )    {        byte[] tempBytes = new byte[                 ( dataLength - maxLength * i > maxLength ) ? maxLength :                                               dataLength - maxLength * i ];        Buffer.BlockCopy( bytes, maxLength * i, tempBytes, 0,                           tempBytes.Length );        byte[] encryptedBytes = rsaCryptoServiceProvider.Encrypt( tempBytes,                                                                  true );                stringBuilder.Append( Convert.ToBase64String( encryptedBytes ) );    }    return stringBuilder.ToString();}public string DecryptString( string inputString, int dwKeySize, string xmlString ){RSACryptoServiceProvider rsaCryptoServiceProvider                             = new RSACryptoServiceProvider( dwKeySize );    rsaCryptoServiceProvider.FromXmlString( xmlString );    int base64BlockSize = ( ( dwKeySize / 8 ) % 3 != 0 ) ?      ( ( ( dwKeySize / 8 ) / 3 ) * 4 ) + 4 : ( ( dwKeySize / 8 ) / 3 ) * 4;    int iterations = inputString.Length / base64BlockSize;     ArrayList arrayList = new ArrayList();    for( int i = 0; i < iterations; i++ )    {        byte[] encryptedBytes = Convert.FromBase64String(              inputString.Substring( base64BlockSize * i, base64BlockSize ) );                Array.Reverse( encryptedBytes );        arrayList.AddRange( rsaCryptoServiceProvider.Decrypt(                             encryptedBytes, true ) );    }    return Encoding.UTF32.GetString( arrayList.ToArray(                               Type.GetType( "System.Byte" ) ) as byte[] );}

Here is one example in MSDN for md5

static void Main(string[] args)        {            string source = "Hello World!";            using (MD5 md5Hash = MD5.Create())            {                string hash = GetMd5Hash(md5Hash, source);                Console.WriteLine("The MD5 hash of " + source + " is: " + hash + ".");                Console.WriteLine("Verifying the hash...");                if (VerifyMd5Hash(md5Hash, source, hash))                {                    Console.WriteLine("The hashes are the same.");                }                else                {                    Console.WriteLine("The hashes are not same.");                }            }        }        static string GetMd5Hash(MD5 md5Hash, string input)        {            // Convert the input string to a byte array and compute the hash.            byte[] data = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(input));            // Create a new Stringbuilder to collect the bytes            // and create a string.            StringBuilder sBuilder = new StringBuilder();            // Loop through each byte of the hashed data             // and format each one as a hexadecimal string.            for (int i = 0; i < data.Length; i++)            {                sBuilder.Append(data[i].ToString("x2"));            }            // Return the hexadecimal string.            return sBuilder.ToString();        }        // Verify a hash against a string.        static bool VerifyMd5Hash(MD5 md5Hash, string input, string hash)        {            // Hash the input.            string hashOfInput = GetMd5Hash(md5Hash, input);            // Create a StringComparer an compare the hashes.            StringComparer comparer = StringComparer.OrdinalIgnoreCase;            if (0 == comparer.Compare(hashOfInput, hash))            {                return true;            }            else            {                return false;            }        }

_{Thursday, July 12, 2012 1:29 PM ✅Answered | 1 vote}

_{Thursday, July 12, 2012 5:49 PM ✅Answered | 38 votes}

Hi,

Check with,

you can change these

static readonly string PasswordHash = "P@@Sw0rd";
static readonly string SaltKey = "S@LT&KEY";
static readonly string VIKey = "@1B2c3D4e5F6g7H8";

for encrypt

  public static string Encrypt(string plainText)
        {
            byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);

            byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256 / 8);
            var symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.Zeros };
            var encryptor = symmetricKey.CreateEncryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
            
            byte[] cipherTextBytes;

            using (var memoryStream = new MemoryStream())
            {
                using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                {
                    cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                    cryptoStream.FlushFinalBlock();
                    cipherTextBytes = memoryStream.ToArray();
                    cryptoStream.Close();
                }
                memoryStream.Close();
            }
            return Convert.ToBase64String(cipherTextBytes);
        }

to decrypt

  public static string Decrypt(string encryptedText)
        {
            byte[] cipherTextBytes = Convert.FromBase64String(encryptedText);
            byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256 / 8);
            var symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.None };

            var decryptor = symmetricKey.CreateDecryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
            var memoryStream = new MemoryStream(cipherTextBytes);
            var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
            byte[] plainTextBytes = new byte[cipherTextBytes.Length];

            int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
            memoryStream.Close();
            cryptoStream.Close();
            return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount).TrimEnd("\0".ToCharArray());
        }

I hope this helps you...

If this post answers your question, please click "Mark As Answer". If this post is helpful please click "Mark as Helpful".

_{Thursday, July 12, 2012 11:32 AM | 1 vote}

http://www.codeproject.com/Articles/14150/Encrypt-and-Decrypt-Data-with-C

_{Thursday, July 12, 2012 11:41 AM | 1 vote}

Look here:

http://social.msdn.microsoft.com/Forums/sa/winformsapplications/thread/5aa93269-b0b0-48c3-941c-ade41f3e3f29

Noam B.

Do not Forget to Vote as Answer/Helpful, please. It encourages us to help you...

_{Thursday, July 12, 2012 11:59 AM | 1 vote}

http://dotnet-snippets.com/dns/encrypt-and-decrypt-strings-SID205.aspx

regards

joon

_{Thursday, July 12, 2012 1:41 PM | 1 vote}

Its simple, you can do like this:

public static string Encrypt(string data)
{
    TripleDESCryptoServiceProvider DES = new TripleDESCryptoServiceProvider();

    DES.Mode = CipherMode.ECB;
    DES.Key = GetKey("a1!B78s!5(");

    DES.Padding = PaddingMode.PKCS7;
    ICryptoTransform DESEncrypt = DES.CreateEncryptor();
    Byte[] Buffer = ASCIIEncoding.ASCII.GetBytes(data);

    return Convert.ToBase64String(DESEncrypt.TransformFinalBlock(Buffer, 0, Buffer.Length));
}

public static string Decrypt(string data)
{
    TripleDESCryptoServiceProvider DES = new TripleDESCryptoServiceProvider();

    DES.Mode = CipherMode.ECB;
    DES.Key = GetKey("a1!B78s!5(");
   
    DES.Padding = PaddingMode.PKCS7;
    ICryptoTransform DESEncrypt = DES.CreateDecryptor();
    Byte[] Buffer = Convert.FromBase64String(data.Replace(" ","+"));

    return Encoding.UTF8.GetString(DESEncrypt.TransformFinalBlock(Buffer, 0, Buffer.Length));
}

And when you want call you make: Encrypt("blablablabla") or Decrypt("891bw01s13")

_{Friday, July 12, 2013 1:22 PM | 2 votes}

what is GetKey("...") actually calling when you do DES.Key. There is not method in your code called GetKey.

_{Wednesday, August 14, 2013 12:54 AM}

@Kris444

Great piece of code, I've used it in a messaging program across my network.
What is this encryption method called? Like if I wanted to decrypt messages in another program, not written in C#, like on a Mac for example, how would I go about doing that?

Thanks :D

_{Sunday, October 26, 2014 3:00 AM}

There's a bug above in the EncryptString() function: You need to comment out the line with:

"RSACryptoServiceProvider here"

This was inadvertently left behind as part of an earlier comment.

_{Thursday, June 18, 2015 9:58 AM}

Hi, can this be used for commercial use?

Thanks

_{Monday, November 21, 2016 1:47 PM}

found the missing peace here:

http://stackoverflow.com/a/30187412/1411724

_{Thursday, July 13, 2017 3:11 AM}

The encryption used here is how many bit encryption

_{Thursday, July 13, 2017 3:17 AM}

I keep getting error saying in quotes "specified initialization vector (IV) does not match the block size for this algorithm."

Please help

_{Friday, May 11, 2018 2:14 PM}

please, what algorithm or method that you had use in this encrypt, decrypt

_{Thursday, May 17, 2018 10:06 AM}

Encrypt/Decrypt is different from encode/decode.

You need passkey to encrypt/decrypt a message so only people who hold the key can get the original message, while you don't need one to encode/decode a message so anyone can get the original one.

Btw, don't needlessly dig an old thread.

_{Wednesday, December 12, 2018 6:45 PM}

I know that this is from 2012 but im getting an error on the GetKey, do you still have the metod?

Thanks

_{Tuesday, May 21, 2019 11:04 PM}

You can use the below method.

public static byte[] GetKey(string strKey)
        {
            byte[] Key = Convert.FromBase64String(strKey);
            return Key;
        }

_{Tuesday, September 24, 2019 12:35 PM}

using System;

using System.Xml;

using System.Security.Cryptography;

using System.IO;

using System.Text;

class

Program

{

privatestaticRSAParameterspublicKey;

privatestaticRSAParametersprivateKey;

publicenumKeySizes

{

SIZE_512 = 512,

SIZE_1024 = 1024,

SIZE_2048 = 2048,

SIZE_4096 = 4096

}

staticvoidMain(string[] args)

{

stringprivateKeyFile = System.AppDomain.CurrentDomain.BaseDirectory + "PrivateKey2.xml";

//string publicKeyFile = System.AppDomain.CurrentDomain.BaseDirectory + "PublicKey2.xml";

////GenerateRsa(privateKeyPath, publicKeyPath, 2048)

stringCiphertext = "PLLX2FuYEYmLD08eD56bgz/xYJJv4Cmtz9S96bm2wgvi4QN8YJ9XggAlkqkwEE+DKPGIY7S2FZc3djswFPn2bv8pNteA6xNcJZEIA4gF57ekBZh6lzoLFXex3kQO0v4g3iWqPfmuN62oEkAhLe3DYaIgt19AX8DJKPEfP/UNyikrAn6YA73kSLePogZHszDXGLMSHrZS1QdLnhEbkVRVQr8iCi2pcsChNR1ZqiObFQp2ErJ6JFqrFEoX8Dbm88Xam/pubtxPX6e5EPxIyB+YmliDVeGm/RL5+LOf7sSospoQPl3oKeummtWHInaLTHEJ58FYOMdEn6oTYykkTiKxsQ==";

byte[] Encrypted = Convert.FromBase64String(Ciphertext);

byte[] decrypted = Decrypt(privateKeyFile, Encrypted);

Console.WriteLine(System.Text.Encoding.UTF8.GetString(decrypted));

Console.ReadLine();

}

privatestaticbyte[] Decrypt(stringprivateKeyFile, byte[] Encrypted)

{

byte[] decodedtxt;

using(varrsa = newRSACryptoServiceProvider((int)2048))

{

rsa.PersistKeyInCsp =

false;

stringprivateKey = File.ReadAllText(privateKeyFile);

rsa.FromXmlString(privateKey);

decodedtxt = rsa.Decrypt(Encrypted,

false);

}

returndecodedtxt;

}

For Encryption below is the code

void Encrypt(public_key);

public voidEncrypt(stringpublic_key)

{

privateRSACryptoServiceProvidercipher = null;

RSACryptoServiceProvider cipher = newRSACryptoServiceProvider();

cipher.FromXmlString(public_key);

byte[] data = Encoding.UTF8.GetBytes(txtUnencrypt.Text);

byte[] cipherText = cipher.Encrypt(data, false);

lblUnencryptMessage.Text = Convert.ToBase64String(cipherText);

}

_{Tuesday, September 24, 2019 12:43 PM}

using System;

using System.Xml;

using System.Security.Cryptography;

using System.IO;

using System.Text;

　

class

Program

{



privatestaticRSAParameterspublicKey;



privatestaticRSAParametersprivateKey;



publicenumKeySizes

    {

        SIZE_512 = 512,

        SIZE_1024 = 1024,

        SIZE_2048 = 2048,

        SIZE_4096 = 4096

    }



staticvoidMain(string[] args)

    {



stringprivateKeyFile = System.AppDomain.CurrentDomain.BaseDirectory + "PrivateKey2.xml";



//string publicKeyFile = System.AppDomain.CurrentDomain.BaseDirectory + "PublicKey2.xml";



////GenerateRsa(privateKeyPath, publicKeyPath, 2048)



stringCiphertext = "PLLX2FuYEYmLD08eD56bgz/xYJJv4Cmtz9S96bm2wgvi4QN8YJ9XggAlkqkwEE+DKPGIY7S2FZc3djswFPn2bv8pNteA6xNcJZEIA4gF57ekBZh6lzoLFXex3kQO0v4g3iWqPfmuN62oEkAhLe3DYaIgt19AX8DJKPEfP/UNyikrAn6YA73kSLePogZHszDXGLMSHrZS1QdLnhEbkVRVQr8iCi2pcsChNR1ZqiObFQp2ErJ6JFqrFEoX8Dbm88Xam/pubtxPX6e5EPxIyB+YmliDVeGm/RL5+LOf7sSospoQPl3oKeummtWHInaLTHEJ58FYOMdEn6oTYykkTiKxsQ==";



byte[] Encrypted = Convert.FromBase64String(Ciphertext);



byte[] decrypted = Decrypt(privateKeyFile, Encrypted);



Console.WriteLine(System.Text.Encoding.UTF8.GetString(decrypted));



Console.ReadLine();

    }



privatestaticbyte[] Decrypt(stringprivateKeyFile, byte[] Encrypted)

    {



byte[] decodedtxt;



using(varrsa = newRSACryptoServiceProvider((int)2048))

        {

            rsa.PersistKeyInCsp =

false;



stringprivateKey = File.ReadAllText(privateKeyFile);

            rsa.FromXmlString(privateKey);

            decodedtxt = rsa.Decrypt(Encrypted,

false);

        }



returndecodedtxt;

　

        }



    }

For Encryption below is the code

void Encrypt(public_key);

public voidEncrypt(stringpublic_key)

{



privateRSACryptoServiceProvidercipher = null;

RSACryptoServiceProvider cipher = newRSACryptoServiceProvider();

cipher.FromXmlString(public_key);



byte[] data = Encoding.UTF8.GetBytes(txtUnencrypt.Text);

byte[] cipherText = cipher.Encrypt(data, false);

lblUnencryptMessage.Text = Convert.ToBase64String(cipherText);

        }

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_{Thursday, April 30, 2020 8:51 PM}

Padding = PaddingMode.None on Decrypt should be set to Zero, as in EncryptOtherwise some text decrypt will fail (such as containing 0)

Last updated on 2012-07-12

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Encrypt and Decrypt a String in c#

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