MD5各种长度加密字符、验证MD5

/// <summary>
/// MD5各种长度加密字符、验证MD5等操作辅助类
/// </summary>
public class MD5Util
{
public MD5Util()
{
}

/// <summary>
/// 获得32位的MD5加密
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static string GetMD5_32(string input)
{
System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create();
byte[] data = md5.ComputeHash(System.Text.Encoding.Default.GetBytes(input));
StringBuilder sb = new StringBuilder();
for (int i = 0; i < data.Length; i++)
{
sb.Append(data[i].ToString("x2"));
}
return sb.ToString();
}

/// <summary>
/// 获得16位的MD5加密
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static string GetMD5_16(string input)
{
return GetMD5_32(input).Substring(8, 16);
}

/// <summary>
/// 获得8位的MD5加密
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static string GetMD5_8(string input)
{
return GetMD5_32(input).Substring(8, 8);
}

/// <summary>
/// 获得4位的MD5加密
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static string GetMD5_4(string input)
{
return GetMD5_32(input).Substring(8, 4);
}

/// <summary>
/// 添加MD5的前缀，便于检查有无篡改
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static string AddMD5Profix(string input)
{
return GetMD5_4(input) + input;
}

/// <summary>
/// 移除MD5的前缀
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static string RemoveMD5Profix(string input)
{
return input.Substring(4);
}

/// <summary>
/// 验证MD5前缀处理的字符串有无被篡改
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static bool ValidateValue(string input)
{
bool res = false;
if (input.Length >= 4)
{
string tmp = input.Substring(4);
if (input.Substring(0, 4) == GetMD5_4(tmp))
{
res = true;
}
}
return res;
}

#region MD5签名验证
/// <summary>
/// 对给定文件路径的文件加上标签
/// </summary>
/// <param name="path">要加密的文件的路径</param>
/// <returns>标签的值</returns>
public static bool AddMD5(string path)
{
bool IsNeed = true;

if (CheckMD5(path)) //已进行MD5处理
IsNeed = false;

try
{
FileStream fsread = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
byte[] md5File = new byte[fsread.Length];
fsread.Read(md5File, 0, (int)fsread.Length); // 将文件流读取到Buffer中
fsread.Close();

if (IsNeed)
{
string result = MD5Buffer(md5File, 0, md5File.Length); // 对Buffer中的字节内容算MD5
byte[] md5 = System.Text.Encoding.ASCII.GetBytes(result); // 将字符串转换成字节数组以便写人到文件中
FileStream fsWrite = new FileStream(path, FileMode.Open, FileAccess.ReadWrite);
fsWrite.Write(md5File, 0, md5File.Length); // 将文件，MD5值 重新写入到文件中。
fsWrite.Write(md5, 0, md5.Length);
fsWrite.Close();
}
else
{
FileStream fsWrite = new FileStream(path, FileMode.Open, FileAccess.ReadWrite);
fsWrite.Write(md5File, 0, md5File.Length);
fsWrite.Close();
}
}
catch
{
return false;
}

return true;
}

/// <summary>
/// 对给定路径的文件进行验证
/// </summary>
/// <param name="path"></param>
/// <returns>是否加了标签或是否标签值与内容值一致</returns>
public static bool CheckMD5(string path)
{
try
{
FileStream get_file = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
byte[] md5File = new byte[get_file.Length]; // 读入文件
get_file.Read(md5File, 0, (int)get_file.Length);
get_file.Close();

string result = MD5Buffer(md5File, 0, md5File.Length - 32); // 对文件除最后32位以外的字节计算MD5，这个32是因为标签位为32位。
string md5 = System.Text.Encoding.ASCII.GetString(md5File, md5File.Length - 32, 32); //读取文件最后32位，其中保存的就是MD5值
return result == md5;
}
catch
{
return false;
}
}

/// <summary>
/// 计算文件的MD5值
/// </summary>
/// <param name="MD5File">MD5签名文件字符数组</param>
/// <param name="index">计算起始位置</param>
/// <param name="count">计算终止位置</param>
/// <returns>计算结果</returns>
private static string MD5Buffer(byte[] MD5File, int index, int count)
{
System.Security.Cryptography.MD5CryptoServiceProvider get_md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
byte[] hash_byte = get_md5.ComputeHash(MD5File, index, count);
string result = System.BitConverter.ToString(hash_byte);

result = result.Replace("-", "");
return result;
}
#endregion

private void Test()
{
string o = "i love u";
o = AddMD5Profix(o);
//o += " ";
Console.WriteLine(o);
Console.WriteLine(ValidateValue(o));

o = RemoveMD5Profix(o);
Console.WriteLine(o);

}
}