RSA生成簽名和驗證簽名

    /// <summary>
    /// RSA注冊碼生成驗證幫助類
    /// </summary>
    public class RSASignature
    {
        /// <summary>
        /// 生成密匙
        /// </summary>
        /// <param name="privateKey">私匙</param>
        /// <param name="publicKey">公匙></param>
        public static void GenerateKeys(out string privateKey, out string publicKey)
        {
            using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
            {
                privateKey = rsa.ToXmlString(true);
                publicKey = rsa.ToXmlString(false);
            }
        }

        /// <summary>
        /// RSA簽名
        /// </summary>
        /// <param name="sSource" >明文</param>
        /// <param name="sPrivateKey" >私匙</param>
        /// <returns>密文</returns>
        public static string CreateSignature(string sSource, string sPrivateKey)
        {
            using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
            {
                rsa.FromXmlString(sPrivateKey);

                RSAPKCS1SignatureFormatter sf = new RSAPKCS1SignatureFormatter(rsa);
                sf.SetHashAlgorithm("SHA256");

                byte[] source = System.Text.ASCIIEncoding.ASCII.GetBytes(sSource);

                SHA256Managed sha2 = new SHA256Managed();
                byte[] result = sha2.ComputeHash(source);
                byte[] signature = sf.CreateSignature(result);

                return Convert.ToBase64String(signature);
            }
        }

        /// <summary>
        /// RSA簽名驗證
        /// </summary>
        /// <param name="sEncryptSource">密文</param>
        /// <param name="sCompareString">需要比較的明文字符串</param>
        /// <param name="sPublicKey">公匙</param>
        /// <returns>是否相同</returns>
        public static bool VerifySignature(string sEncryptSource, string sCompareString, string sPublicKey)
        {
            try
            {
                using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
                {
                    rsa.FromXmlString(sPublicKey);

                    RSAPKCS1SignatureDeformatter df = new RSAPKCS1SignatureDeformatter(rsa);
                    df.SetHashAlgorithm("SHA256");

                    byte[] signature = Convert.FromBase64String(sEncryptSource);

                    SHA256Managed sha2 = new SHA256Managed();
                    byte[] compareByte = sha2.ComputeHash(ASCIIEncoding.ASCII.GetBytes(sCompareString));

                    return df.VerifySignature(compareByte, signature);
                }
            }
            catch (Exception)
            {
                return false;
            }
        }
    }

改進：將SHA1改為SHA256，提高安全性
測試

        string publicKey = "<RSAKeyValue><Modulus>2DF7PLozXLLJb2vTknucTOK8+ucjYlVFOThnRwqULjeSuA2ZlReaBVXRy8PonVkXXfN2tjosy2ToTwHNX4UQP5kkEbBWYk8knOZPF/96OI2GfjGYnwNUT0CIKHda8B8ztfh1LQanNOCrrByHIuGTORL1WR2hlbaIHRrOIRkeOMc=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";
        string privateKey = "<RSAKeyValue><Modulus>2DF7PLozXLLJb2vTknucTOK8+ucjYlVFOThnRwqULjeSuA2ZlReaBVXRy8PonVkXXfN2tjosy2ToTwHNX4UQP5kkEbBWYk8knOZPF/96OI2GfjGYnwNUT0CIKHda8B8ztfh1LQanNOCrrByHIuGTORL1WR2hlbaIHRrOIRkeOMc=</Modulus><Exponent>AQAB</Exponent><P>+WLUzPp7LeMmXaZ3Ebcw6+Ks1HA6XlkpfhLS4DOnViw2O1V/8EXFO77KwFLSwlCzfXo1LN0JuTEsacGdU3f5yw==</P><Q>3e1K+J8Ns4UrbhQzgIbyGf8JX+VaETWClJSq9vEXelHGfG9/+5bbGvnF4Wo1c/Kdkuz5IQHfYbuTgMU4LpVNdQ==</Q><DP>bV/6IrhMo/B22CX1HNDyZNIyqK1b/BswxnltASXGY1XapyU1imSfPzfLZpQsmUqZnhOmFLoQ1KcLaoqe/IenBw==</DP><DQ>J3CndT3XEoNlL3/5kyroVcRkZx18fzhyR3OQWqiIEp3711t9dDngIJApIaFddIi2hkkFEV+i0lyinyztiiHQjQ==</DQ><InverseQ>Fdk/2JOc/gj7YKsKgMEEVC0+X+WlAMhF+PJVgs188vIQSuXJTRi8Z4A214fvX49s2G81Th7KdYUWCvBAeD153Q==</InverseQ><D>wgJFkY2XIgzfb7nXt5BuByFCbfaWblwPLvZK2BnKOF9urvSlaoIvmbIV/0HjsbCNo6YkVguGv0/imWQIpTuIA6O5S1NX/dbYLp2/rSNl0/xSB5ZjX06VAYbeIsB7YWw87+35K8DrIrlZDMP4Mk6h+pawdgLTtIo/tjTpBhCfB+E=</D></RSAKeyValue>";

        private void btnCreateRegister_Click(object sender, EventArgs e)
        {
            if (!string.IsNullOrEmpty(txtComputerInfo.Text))
            {
                txtRegister.Text = RSASignature.CreateSignature(txtComputerInfo.Text.Trim(), privateKey);
            }
            else
            {
                MessageBox.Show("請輸入機器碼！");
                txtComputerInfo.Focus();
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            bool result = RSASignature.VerifySignature(txtRegister.Text, txtComputerInfo.Text.Trim(), publicKey);
            MessageBox.Show(result.ToString());
        }