//明文密碼由字符串轉換為byte數(shù)組
byte[] clearBytes =Encoding.Default.GetBytes("123");

//由明文的byte數(shù)組計算出MD5密文byte數(shù)組
byte[] hashedBytes = ((HashAlgorithm)CryptoConfig.CreateFromName("MD5")).ComputeHash(clearBytes);
//把byte數(shù)組轉換為字符串后返回，BitConverter用于將基礎數(shù)據(jù)類型與字節(jié)數(shù)組相互轉換
string result = BitConverter.ToString(hashedBytes).Replace("-", "");

Console.Write(result);

byte[] clearBytes = Encoding.Default.GetBytes("123");
byte[] hashedBytes =  MD5.Create().ComputeHash(clearBytes);

StringBuilder sBuilder = new StringBuilder();
for (int i = 0; i < hashedBytes.Length; i++)
{
    sBuilder.Append(hashedBytes[i].ToString("x2"));
}
string result = sBuilder.ToString();
Console.Write(result);

byte[] clearBytes = Encoding.Default.GetBytes("123");
byte[] hashedBytes = new MD5CryptoServiceProvider().ComputeHash(clearBytes);
string result = "";
for (int i = 0; i < hashedBytes.Length; i++)
    result += hashedBytes[i].ToString("X").PadLeft(2, '0');

Console.Write(result);

FormAuthentication.HashPasswordForStoringInConfigFile(str,"MD5")//或者“SHA1”

string GetFileHash(string path)
{
    var hash = MD5.Create();//SHA1.Create();
    var stream = new FileStream(path, FileMode.Open);
    byte[] hashByte = hash.ComputeHash(stream);
    stream.Close();
    return BitConverter.ToString(hashByte).Replace("-", "");
}

public static string strKey = "abcdefgh";//注意：這里的密鑰sKey必須能轉為8個byte，即輸入密鑰為8半角個字符或者4個全角字符或者4個漢字的字符串
public static string strIV = "ijklmnop";

// 加密
public static string Encrypt(string _strQ)
{
    byte[] buffer = Encoding.UTF8.GetBytes(_strQ);
    MemoryStream ms = new MemoryStream();
    DESCryptoServiceProvider des = new DESCryptoServiceProvider();
    CryptoStream encStream = new CryptoStream(ms, des.CreateEncryptor(Encoding.UTF8.GetBytes(strKey), Encoding.UTF8.GetBytes(strIV)), CryptoStreamMode.Write);
    encStream.Write(buffer, 0, buffer.Length);
    encStream.FlushFinalBlock();
    return Convert.ToBase64String(ms.ToArray());
}

// 解密
public static string Decrypt(string _strQ)
{
    byte[] buffer = Convert.FromBase64String(_strQ);
    MemoryStream ms = new MemoryStream();
    DESCryptoServiceProvider des = new DESCryptoServiceProvider();
    CryptoStream encStream = new CryptoStream(ms, des.CreateDecryptor(Encoding.UTF8.GetBytes(strKey), Encoding.UTF8.GetBytes(strIV)), CryptoStreamMode.Write);
    encStream.Write(buffer, 0, buffer.Length);
    encStream.FlushFinalBlock();
    return Encoding.UTF8.GetString(ms.ToArray());
}

/// 

/// 獲取加密所使用的key，RSA算法是一種非對稱密碼算法，所謂非對稱，就是指該算法需要一對密鑰，使用其中一個加密，則需要用另一個才能解密。
/// 
public static void GetKey()
{
    string PublicKey = string.Empty;
    string PrivateKey = string.Empty;
    RSACryptoServiceProvider rSACryptoServiceProvider = new RSACryptoServiceProvider();
    PublicKey = rSACryptoServiceProvider.ToXmlString(false);
    // 獲取公匙，用于加密
    PrivateKey = rSACryptoServiceProvider.ToXmlString(true);
    // 獲取公匙和私匙，用于解密

    //Console.WriteLine("PublicKey is {0}", PublicKey);        // 輸出公匙
    //Console.WriteLine("PrivateKey is {0}", PrivateKey);     // 輸出密匙
    //密匙中含有公匙，公匙是根據(jù)密匙進行計算得來的。

    using (StreamWriter streamWriter = new StreamWriter("PublicKey.xml"))
    {
        streamWriter.Write(rSACryptoServiceProvider.ToXmlString(false));// 將公匙保存到運行目錄下的PublicKey
    }
    using (StreamWriter streamWriter = new StreamWriter("PrivateKey.xml"))
    {
        streamWriter.Write(rSACryptoServiceProvider.ToXmlString(true)); // 將公匙&私匙保存到運行目錄下的PrivateKey
    }
}

/// 

/// 加密
/// 
private static string Encryption(string str)
{
    RSACryptoServiceProvider rSACryptoServiceProvider = new RSACryptoServiceProvider();
    using (StreamReader streamReader = new StreamReader("PublicKey.xml")) // 讀取運行目錄下的PublicKey.xml
    {
        rSACryptoServiceProvider.FromXmlString(streamReader.ReadToEnd()); // 將公匙載入進RSA實例中
    }

    byte[] buffer = Encoding.UTF8.GetBytes(str); // 將明文轉換為byte[]

    // 加密后的數(shù)據(jù)就是一個byte[] 數(shù)組,可以以 文件的形式保存 或 別的形式(網(wǎng)上很多教程,使用Base64進行編碼化保存)
    byte[] EncryptBuffer = rSACryptoServiceProvider.Encrypt(buffer, false); // 進行加密
    return Convert.ToBase64String(EncryptBuffer); // 如果使用base64進行明文化，在解密時 需要再次將base64 轉換為byte[]
}

/// 

/// 解密
/// 
private static string Decrypt(string strEncryptBase64)
{
    RSACryptoServiceProvider rSACryptoServiceProvider = new RSACryptoServiceProvider();
    using (StreamReader streamReader = new StreamReader("PrivateKey.xml")) // 讀取運行目錄下的PrivateKey.xml
    {
        rSACryptoServiceProvider.FromXmlString(streamReader.ReadToEnd()); // 將私匙載入進RSA實例中
    }

    byte[] buffer = Convert.FromBase64String(strEncryptBase64);
    // 解密后得到一個byte[] 數(shù)組
    byte[] DecryptBuffer = rSACryptoServiceProvider.Decrypt(buffer, false); // 進行解密
    string str = Encoding.UTF8.GetString(DecryptBuffer); // 將byte[]轉換為明文

    return str;
}