您必须使用System.Security.Cryptography来使用命名空间;usehash是bool类型，true或false。字符串变量“key”对于加密和解密应该是相同的

//Encryption
public string EncryptText(string toEncrypt, bool useHashing)
    {
        try
        {
            byte[] keyArray;
            byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);

            string key = "String Key Value"; //Based on this key stirng is encrypting
            //System.Windows.Forms.MessageBox.Show(key);
            //If hashing use get hashcode regards to your key
            if (useHashing)
            {
                MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                //Always release the resources and flush data
                //of the Cryptographic service provide. Best Practice

                hashmd5.Clear();
            }
            else
                keyArray = UTF8Encoding.UTF8.GetBytes(key);

            TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
            //set the secret key for the tripleDES algorithm
            tdes.Key = keyArray;
            //mode of operation. there are other 4 modes. We choose ECB(Electronic code Book)
            tdes.Mode = CipherMode.ECB;
            //padding mode(if any extra byte added)
            tdes.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdes.CreateEncryptor();
            //transform the specified region of bytes array to resultArray
            byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0,          toEncryptArray.Length);
            //Release resources held by TripleDes Encryptor
            tdes.Clear();
            //Return the encrypted data into unreadable string format
            return Convert.ToBase64String(resultArray, 0, resultArray.Length);
        }
        catch (Exception e)
        {
            throw e;
        }
    }

    //Decryption
    public string DecryptText(string cipherString, bool useHashing)
    {

        try
        {
            byte[] keyArray;
            //get the byte code of the string

            byte[] toEncryptArray = Convert.FromBase64String(cipherString);

            string key = "String Key Value"; //Based on this key string is decrypted

            if (useHashing)
            {
                //if hashing was used get the hash code with regards to your key
                MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                //release any resource held by the MD5CryptoServiceProvider

                hashmd5.Clear();
            }
            else
            {
                //if hashing was not implemented get the byte code of the key
                keyArray = UTF8Encoding.UTF8.GetBytes(key);
            }

            TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
            //set the secret key for the tripleDES algorithm
            tdes.Key = keyArray;
            //mode of operation. there are other 4 modes.
            //We choose ECB(Electronic code Book)

            tdes.Mode = CipherMode.ECB;
            //padding mode(if any extra byte added)
            tdes.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdes.CreateDecryptor();
            byte[] resultArray = cTransform.TransformFinalBlock
                    (toEncryptArray, 0, toEncryptArray.Length);
            //Release resources held by TripleDes Encryptor
            tdes.Clear();
            //return the Clear decrypted TEXT
            return UTF8Encoding.UTF8.GetString(resultArray);
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

参考c#中加密和解密字符串，我找到了一个很好的解决方案:

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

对于加密

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);
}

对解密

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());
}

我有一个名为X509Crypto的开源项目，它利用证书来加密和解密字符串。它很容易使用。下面是一个如何使用它的例子:

1. 2 .使用X509Crypto命令行生成新的加密证书和密钥对

>x509crypto.exe
X509Crypto> makecert -context user -keysize medium -alias myvault

Certificate with thumbprint B31FE7E7AE5229F8186782742CF579197FA859FD was added to X509Alias "myvault" in the user X509Context

X509Crypto>

2. 使用Encrypt CLI命令向新的X509Alias添加一个秘密

X509Crypto> encrypt -text -alias myvault -context user -secret apikey -in "80EAF03248965AC2B78090"

Secret apikey has been added to X509Alias myvault in the user X509Context

X509Crypto>

3.在程序中引用该秘密

一旦你建立了一个X509Alias并添加了你的秘密，在你的程序中使用Org检索它们是很简单的。X509Crypto nuget包安装:

using Org.X509Crypto;

namespace SampleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var Alias = new X509Alias(@"myvault", X509Context.UserReadOnly);
            var apiKey = Alias.RecoverSecret(@"apikey");
        }
    }
}

我在这里复制了一个类似问题的答案:c#的简单双向加密。

基于多个答案和评论。

加密文本前的随机初始化向量(@jbtule) 使用TransformFinalBlock()代替MemoryStream (@RenniePet) 没有预填充键，以避免任何人复制和粘贴灾难 正确处理和使用模式

代码:

/// <summary>
/// Simple encryption/decryption using a random initialization vector
/// and prepending it to the crypto text.
/// </summary>
/// <remarks>Based on multiple answers in https://stackoverflow.com/questions/165808/simple-two-way-encryption-for-c-sharp </remarks>
public class SimpleAes : IDisposable
{
    /// <summary>
    ///     Initialization vector length in bytes.
    /// </summary>
    private const int IvBytes = 16;

    /// <summary>
    ///     Must be exactly 16, 24 or 32 characters long.
    /// </summary>
    private static readonly byte[] Key = Convert.FromBase64String("FILL ME WITH 16, 24 OR 32 CHARS");

    private readonly UTF8Encoding _encoder;
    private readonly ICryptoTransform _encryptor;
    private readonly RijndaelManaged _rijndael;

    public SimpleAes()
    {
        _rijndael = new RijndaelManaged {Key = Key};
        _rijndael.GenerateIV();
        _encryptor = _rijndael.CreateEncryptor();
        _encoder = new UTF8Encoding();
    }

    public string Decrypt(string encrypted)
    {
        return _encoder.GetString(Decrypt(Convert.FromBase64String(encrypted)));
    }

    public void Dispose()
    {
        _rijndael.Dispose();
        _encryptor.Dispose();
    }

    public string Encrypt(string unencrypted)
    {
        return Convert.ToBase64String(Encrypt(_encoder.GetBytes(unencrypted)));
    }

    private byte[] Decrypt(byte[] buffer)
    {
        // IV is prepended to cryptotext
        byte[] iv = buffer.Take(IvBytes).ToArray();
        using (ICryptoTransform decryptor = _rijndael.CreateDecryptor(_rijndael.Key, iv))
        {
            return decryptor.TransformFinalBlock(buffer, IvBytes, buffer.Length - IvBytes);
        }
    }

    private byte[] Encrypt(byte[] buffer)
    {
        // Prepend cryptotext with IV
        byte[] inputBuffer = _rijndael.IV.Concat(buffer).ToArray();
        return _encryptor.TransformFinalBlock(inputBuffer, IvBytes, buffer.Length);
    }
}

如果您正在使用ASP。你现在可以使用。Net 4.0以后的内置功能了。

System.Web.Security.MachineKey

. net 4.5有MachineKey.Protect()和MachineKey.Unprotect()。

. net 4.0有MachineKey.Encode()和MachineKey.Decode()。你应该将MachineKeyProtection设置为“All”。

ASP之外。Net这个类似乎在每次应用程序重新启动时都会生成一个新键，所以不起作用。在ILSpy中，如果缺少适当的app.settings，它就会生成自己的默认值。你可以在ASP.Net之外设置。

我还没找到非asp的。系统外的净等值。网络名称空间。

            using System;
            using System.Collections.Generic;
            using System.Text;
            using System.Text.RegularExpressions;  // This is for password validation
            using System.Security.Cryptography;
            using System.Configuration;  // This is where the hash functions reside

            namespace BullyTracker.Common
            {
                public class HashEncryption
                {
                    //public string GenerateHashvalue(string thisPassword)
                    //{
                    //    MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
                    //    byte[] tmpSource;
                    //    byte[] tmpHash;

                    //    tmpSource = ASCIIEncoding.ASCII.GetBytes(thisPassword); // Turn password into byte array
                    //    tmpHash = md5.ComputeHash(tmpSource);

                    //    StringBuilder sOutput = new StringBuilder(tmpHash.Length);
                    //    for (int i = 0; i < tmpHash.Length; i++)
                    //    {
                    //        sOutput.Append(tmpHash[i].ToString("X2"));  // X2 formats to hexadecimal
                    //    }
                    //    return sOutput.ToString();
                    //}
                    //public Boolean VerifyHashPassword(string thisPassword, string thisHash)
                    //{
                    //    Boolean IsValid = false;
                    //    string tmpHash = GenerateHashvalue(thisPassword); // Call the routine on user input
                    //    if (tmpHash == thisHash) IsValid = true;  // Compare to previously generated hash
                    //    return IsValid;
                    //}
                    public string GenerateHashvalue(string toEncrypt, bool useHashing)
                    {
                        byte[] keyArray;
                        byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);

                        System.Configuration.AppSettingsReader settingsReader = new AppSettingsReader();
                        // Get the key from config file
                        string key = (string)settingsReader.GetValue("SecurityKey", typeof(String));
                        //System.Windows.Forms.MessageBox.Show(key);
                        if (useHashing)
                        {
                            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                            keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                            hashmd5.Clear();
                        }
                        else
                            keyArray = UTF8Encoding.UTF8.GetBytes(key);

                        TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
                        tdes.Key = keyArray;
                        tdes.Mode = CipherMode.ECB;
                        tdes.Padding = PaddingMode.PKCS7;

                        ICryptoTransform cTransform = tdes.CreateEncryptor();
                        byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
                        tdes.Clear();
                        return Convert.ToBase64String(resultArray, 0, resultArray.Length);
                    }
                    /// <summary>
                    /// DeCrypt a string using dual encryption method. Return a DeCrypted clear string
                    /// </summary>
                    /// <param name="cipherString">encrypted string</param>
                    /// <param name="useHashing">Did you use hashing to encrypt this data? pass true is yes</param>
                    /// <returns></returns>
                    public string Decrypt(string cipherString, bool useHashing)
                    {
                        byte[] keyArray;
                        byte[] toEncryptArray = Convert.FromBase64String(cipherString);

                        System.Configuration.AppSettingsReader settingsReader = new AppSettingsReader();
                        //Get your key from config file to open the lock!
                        string key = (string)settingsReader.GetValue("SecurityKey", typeof(String));

                        if (useHashing)
                        {
                            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                            keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                            hashmd5.Clear();
                        }
                        else
                            keyArray = UTF8Encoding.UTF8.GetBytes(key);

                        TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
                        tdes.Key = keyArray;
                        tdes.Mode = CipherMode.ECB;
                        tdes.Padding = PaddingMode.PKCS7;

                        ICryptoTransform cTransform = tdes.CreateDecryptor();
                        byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

                        tdes.Clear();
                        return UTF8Encoding.UTF8.GetString(resultArray);
                    }


                }

            }