Sowmya Sirsi

Sowmya Sirsi

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How to store the Public and private key in xml using RSA algo

Dec 16 2021 10:30 AM

Hi Team,

How to store the public and private key in xml file and extract the same key  to create signature/ verify signature.

CODE:

public string SignXMLD(string rawxml) ///Signature Creation Method
{
    //Declaring variables
    string SourceData;
    byte[] tmpSource;
    byte[] tmpHash;
    SourceData = "AgencyBanking";
    ////Declaring variables
    //create a byte array from source data
    tmpSource = ASCIIEncoding.ASCII.GetBytes(SourceData);
    Console.WriteLine("Key Pairs are generating .............please wait for few moments.......");
    //RSAKeyPairGenerator generates the RSA key pair based on the random number and strength of the key required
    RsaKeyPairGenerator rsaKeyPairGen = new RsaKeyPairGenerator();
    rsaKeyPairGen.Init(new KeyGenerationParameters(new SecureRandom(), 2048));
    keyPair = rsaKeyPairGen.GenerateKeyPair();
    //Extracting the Private key from pair
    RsaKeyParameters PrivateKey = (RsaKeyParameters)keyPair.Private;
    //Store the private key in xml file   
    //How to store the private key generated from keypair into xml file and extract 
    //the same key and use it to generate the signature                                                                
    string str = PrivateKey.FromXmlString(true); 
    //Generate the Digital Signature 
    ISigner sign = SignerUtilities.GetSigner(PkcsObjectIdentifiers.Sha1WithRsaEncryption.Id);
    sign.Init(true, PrivateKey);
    sign.BlockUpdate(tmpSource, 0, tmpSource.Length);
    byte[] signature = sign.GenerateSignature();
    string xyz = Convert.ToBase64String(signature);
    Console.WriteLine();
    Console.WriteLine("The Digital Signature is : ");
    Console.WriteLine(ByteArrayToString(signature));
    XmlDocument objdocument = new XmlDocument();
    objdocument.LoadXml(rawxml);
    XmlDocument newXmlr = new XmlDocument();
    newXmlr.LoadXml("<root></root>");
    XmlNode rootNoder = newXmlr.ImportNode(objdocument.DocumentElement, true);
    newXmlr.DocumentElement.AppendChild(rootNoder);
    XmlDocument newXmlnew = new XmlDocument();
    XmlNode root = newXmlr.DocumentElement;
    //Create a new node.
    XmlElement elem = newXmlr.CreateElement("Signature");
    elem.InnerText = xyz;
    root.AppendChild(elem);
    string strXML = root.OuterXml;

    return strXML;

}

static string ByteArrayToString(byte[] arrInput)
{
    int i;
    StringBuilder sOutput = new StringBuilder(arrInput.Length);
    for (i = 0; i < arrInput.Length; i++)
    {
        sOutput.Append(arrInput[i].ToString("X".ToLower()));
    }
    return sOutput.ToString();
}

public bool SignXMLDResponse(string rawxml) //// SIgnature Verification Method
{
    //Declaring variables
    string SourceData;
    byte[] tmpSource;
    byte[] tmpHash;
    SourceData = "AgencyBanking";
    //create a byte array from source data
    tmpSource = ASCIIEncoding.ASCII.GetBytes(SourceData);
    Console.WriteLine();
    Console.WriteLine();
    Console.WriteLine("Key Pairs are generating .............please wait for few moments.......");
    //Extracting the Private key from pair
    bool status = false;
    RsaKeyParameters PublicKey = (RsaKeyParameters)keyPair.Public;

    //Verification of the Digital Signature
    try
    {
        XmlDocument newXmlnew = new XmlDocument();
        newXmlnew.LoadXml(rawxml);
        XmlNodeList nodeList = newXmlnew.GetElementsByTagName("Signature");
        foreach (XmlNode node in nodeList)
        {
            string s = node.InnerXml;
            byte[] signaturenew = Convert.FromBase64String(s);
            ISigner sign1 = SignerUtilities.GetSigner(PkcsObjectIdentifiers.Sha1WithRsaEncryption.Id);
            sign1.Init(false, PublicKey);
            sign1.BlockUpdate(tmpSource, 0, tmpSource.Length);
            status = sign1.VerifySignature(signaturenew);
        }
    }
    catch (Exception e)
    {
        Console.WriteLine("The Digital Signature is Valid" + e.Message + e.StackTrace);
    }
    return status;
}

Please assist me regarding this

Thanks


Answers (3)