密码学系列——数字签名(c# 代码实操)

前言

结合消息摘要、非对称加密、数字签名三篇，进行代码实操。

代码完整，可复制运行。

正文

代码如下:

public class SignatureHelper
{
	/// <summary>
	/// RSA签名
	/// </summary>
	/// <param name="content">数据</param>
	/// <param name="privateKey">RSA密钥</param>
	/// <returns></returns>
	public static string rsaSign(string content, string privateKey)
	{ 
		if (string.IsNullOrEmpty(content))
		{
			throw new ArgumentNullException(nameof(content));
		}
		var rsaParameters = privateKeyToRSAParameters(privateKey);
		using (var rsa = RSA.Create())
		{
			rsa.ImportParameters(rsaParameters);
			return Base64.ToBase64String(rsa.SignData(Encoding.UTF8.GetBytes(content), HashAlgorithmName.SHA1, RSASignaturePadding.Pkcs1));
		}
	}
	private static RSAParameters privateKeyToRSAParameters(string key)
	{
		var rsaParameters = new RSAParameters();
		using (BinaryReader binr = new BinaryReader(new MemoryStream(Convert.FromBase64String(key))))
		{
			byte bt = 0;
			ushort twobytes = 0;
			twobytes = binr.ReadUInt16();
			if (twobytes == 0x8130)
				binr.ReadByte();
			else if (twobytes == 0x8230)
				binr.ReadInt16();
			else
				throw new Exception("Unexpected value read binr.ReadUInt16()");

			twobytes = binr.ReadUInt16();
			if (twobytes != 0x0102)
				throw new Exception("Unexpected version");

			bt = binr.ReadByte();
			if (bt != 0x00)
				throw new Exception("Unexpected value read binr.ReadByte()");

			rsaParameters.Modulus = binr.ReadBytes(GetIntegerSize(binr));
			rsaParameters.Exponent = binr.ReadBytes(GetIntegerSize(binr));
			rsaParameters.D = binr.ReadBytes(GetIntegerSize(binr));
			rsaParameters.P = binr.ReadBytes(GetIntegerSize(binr));
			rsaParameters.Q = binr.ReadBytes(GetIntegerSize(binr));
			rsaParameters.DP = binr.ReadBytes(GetIntegerSize(binr));
			rsaParameters.DQ = binr.ReadBytes(GetIntegerSize(binr));
			rsaParameters.InverseQ = binr.ReadBytes(GetIntegerSize(binr));
		}
		return rsaParameters;
	}

	private static bool CompareBytearrays(byte[] a, byte[] b)
	{
		if (a.Length != b.Length)
			return false;
		int i = 0;
		foreach (byte c in a)
		{
			if (c != b[i])
				return false;
			i++;
		}
		return true;
	}
	private static RSAParameters publicKeyToRSAParameters(string publicKeyString)
	{
		// encoded OID sequence for  PKCS #1 rsaEncryption szOID_RSA_RSA = "1.2.840.113549.1.1.1"
		byte[] seqOid = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
		byte[] seq = new byte[15];

		var x509Key = Convert.FromBase64String(publicKeyString);

		// ---------  Set up stream to read the asn.1 encoded SubjectPublicKeyInfo blob  ------
		using (MemoryStream mem = new MemoryStream(x509Key))
		{
			using (BinaryReader binr = new BinaryReader(mem))  //wrap Memory Stream with BinaryReader for easy reading
			{
				byte bt = 0;
				ushort twobytes = 0;

				twobytes = binr.ReadUInt16();
				if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
					binr.ReadByte();    //advance 1 byte
				else if (twobytes == 0x8230)
					binr.ReadInt16();   //advance 2 bytes
				else
				   throw new Exception("Unexpected value read binr.ReadUInt16()");

				seq = binr.ReadBytes(15);       //read the Sequence OID
				if (!CompareBytearrays(seq, seqOid))    //make sure Sequence for OID is correct
					throw new Exception("Unexpected value read binr.ReadUInt16()");

				twobytes = binr.ReadUInt16();
				if (twobytes == 0x8103) //data read as little endian order (actual data order for Bit String is 03 81)
					binr.ReadByte();    //advance 1 byte
				else if (twobytes == 0x8203)
					binr.ReadInt16();   //advance 2 bytes
				else
					throw new Exception("Unexpected value read binr.ReadUInt16()");

				bt = binr.ReadByte();
				if (bt != 0x00)     //expect null byte next
					throw new Exception("Unexpected value read binr.ReadUInt16()");

				twobytes = binr.ReadUInt16();
				if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
					binr.ReadByte();    //advance 1 byte
				else if (twobytes == 0x8230)
					binr.ReadInt16();   //advance 2 bytes
				else
					throw new Exception("Unexpected value read binr.ReadUInt16()");
				twobytes = binr.ReadUInt16();
				byte lowbyte = 0x00;
				byte highbyte = 0x00;

				if (twobytes == 0x8102) //data read as little endian order (actual data order for Integer is 02 81)
					lowbyte = binr.ReadByte();  // read next bytes which is bytes in modulus
				else if (twobytes == 0x8202)
				{
					highbyte = binr.ReadByte(); //advance 2 bytes
					lowbyte = binr.ReadByte();
				}
				else
					throw new Exception("Unexpected value read binr.ReadUInt16()");
				byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };   //reverse byte order since asn.1 key uses big endian order
				int modsize = BitConverter.ToInt32(modint, 0);

				int firstbyte = binr.PeekChar();
				if (firstbyte == 0x00)
				{   //if first byte (highest order) of modulus is zero, don't include it
					binr.ReadByte();    //skip this null byte
					modsize -= 1;   //reduce modulus buffer size by 1
				}

				byte[] modulus = binr.ReadBytes(modsize);   //read the modulus bytes

				if (binr.ReadByte() != 0x02)            //expect an Integer for the exponent data
					throw new Exception("Unexpected value read binr.ReadUInt16()");
				int expbytes = (int)binr.ReadByte();        // should only need one byte for actual exponent data (for all useful values)
				byte[] exponent = binr.ReadBytes(expbytes);

				// ------- create RSACryptoServiceProvider instance and initialize with public key -----
				var rsa = RSA.Create();
				RSAParameters rsaKeyInfo = new RSAParameters
				{
					Modulus = modulus,
					Exponent = exponent
				};
				return rsaKeyInfo;
			}
		}
	}

	private static int GetIntegerSize(BinaryReader binr)
	{
		byte bt = 0;
		int count = 0;
		bt = binr.ReadByte();
		if (bt != 0x02)
			return 0;
		bt = binr.ReadByte();

		if (bt == 0x81)
			count = binr.ReadByte();
		else
		if (bt == 0x82)
		{
			var highbyte = binr.ReadByte();
			var lowbyte = binr.ReadByte();
			byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
			count = BitConverter.ToInt32(modint, 0);
		}
		else
		{
			count = bt;
		}

		while (binr.ReadByte() == 0x00)
		{
			count -= 1;
		}
		binr.BaseStream.Seek(-1, SeekOrigin.Current);
		return count;
	}

	/// <summary>
	/// 验证数字签名
	/// </summary>
	/// <param name="plaintext">明文</param>
	/// <param name="signedData">数字签名</param>
	/// <param name="publicKey">公钥</param>
	/// <returns></returns>
	public static bool verifySigned(string plaintext, string signedData, string publicKey)
	{
		if (string.IsNullOrEmpty(plaintext))
		{
			throw new ArgumentNullException(nameof(plaintext));
		}

		if (string.IsNullOrEmpty(signedData))
		{
			throw new ArgumentNullException(nameof(signedData));
		}

		using (var rsa = RSA.Create())
		{
			var rsaParameters = publicKeyToRSAParameters(publicKey);
			rsa.ImportParameters(rsaParameters);
			return rsa.VerifyData(Encoding.UTF8.GetBytes(plaintext), Convert.FromBase64String(signedData), HashAlgorithmName.SHA1, RSASignaturePadding.Pkcs1);
		}
	}
}

测试:

static void Main(string[] args)
{
	RSAKeyParameter rsa1=Pkcs1(1024);
	Console.WriteLine("公钥为:"+rsa1.PublicKey+"私钥为:"+rsa1.PrivateKey);
	string input = "奥氏的家园";
	Console.WriteLine("内容:" + input);
	var signData=SignatureHelper.rsaSign(input,rsa1.PrivateKey);
	Console.WriteLine("数字签名为:" + signData);
	var isSuccess=SignatureHelper.verifySigned(input, signData,rsa1.PublicKey);
	Console.WriteLine("验证是否成功:" + isSuccess);
	Console.ReadKey();
}
/// <summary>
/// pkcs1 rsa 加密
/// </summary>
/// <param name="size">秘钥长度，一般为1024的倍数</param>
/// <param name="pemFormat">是否转换成大小</param>
/// <returns></returns>
public static RSAKeyParameter Pkcs1(int size, bool pemFormat = false)
{
	var keyGenerator = GeneratorUtilities.GetKeyPairGenerator("RSA");
	keyGenerator.Init(new KeyGenerationParameters(new SecureRandom(), size));
	var keyPair = keyGenerator.GenerateKeyPair();
	var subjectPublicKeyInfo=SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(keyPair.Public);
	var privateKeyInfo= PrivateKeyInfoFactory.CreatePrivateKeyInfo(keyPair.Private);
	if (!pemFormat)
	{
		return new RSAKeyParameter
		{
			PrivateKey = Base64.ToBase64String(privateKeyInfo.ParsePrivateKey().GetEncoded()),
			PublicKey = Base64.ToBase64String(subjectPublicKeyInfo.GetEncoded())
		};
	}
	var rsaKey = new RSAKeyParameter();
	using (var sw=new StringWriter())
	{
		var pWrt = new PemWriter(sw);
		pWrt.WriteObject(keyPair.Private);
		pWrt.Writer.Close();
		rsaKey.PrivateKey = sw.ToString();
	}
	using (var sw = new StringWriter())
	{
		var pWrt = new PemWriter(sw);
		pWrt.WriteObject(keyPair.Public);
		pWrt.Writer.Close();
		rsaKey.PublicKey = sw.ToString();
	}
	return rsaKey;
}