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Android App using C#

Suraj Binorkar

Suraj Binorkar
8y
632
1
Hi I want to know how do i create Android App using C# xamarin, I installed vs2015 Microsoft provide free template of xamarin which helps to create basic android app using C#, If anyone idea about it how to create and run this application please let me know :) Thanks in Advance 
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Emily Foster

Emily Foster

758 875 0 Feb 25

To insert a digital signature using a digital certificate at runtime into a PDF without user intervention, you can utilize a programming language like Java along with libraries that support digital signatures like Bouncy Castle or iText. Here's a high-level overview of the process:

1. Load the PDF document that you want to sign.

2. Load the digital certificate from the ".pfx" file using the provided password.

3. Create a digital signature with the certificate's private key.

4. Add the digital signature to each page of the PDF document.

Below is a simplified example using Java and the iText library to demonstrate how you can digitally sign a PDF at runtime:


import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import com.itextpdf.text.pdf.PdfSignatureAppearance;
import java.io.FileInputStream;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.cert.Certificate;

public class DigitalSignatureExample {
    public static void main(String[] args) {
        try {
            String pdfFilePath = "path/to/input.pdf";
            String outputPdfFilePath = "path/to/output.pdf";
            String pfxFilePath = "path/to/ANY NAME.PFX";
            String password = "PASSWORD";

            KeyStore ks = KeyStore.getInstance("PKCS12");
            ks.load(new FileInputStream(pfxFilePath), password.toCharArray());

            String alias = (String) ks.aliases().nextElement();
            PrivateKey privateKey = (PrivateKey) ks.getKey(alias, password.toCharArray());
            Certificate[] chain = ks.getCertificateChain(alias);

            PdfReader reader = new PdfReader(pdfFilePath);
            PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(outputPdfFilePath));
            PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
            
            appearance.setCertificate(chain[0]);
            appearance.setReason("Digitally signed by me");
            appearance.setLocation("Location");
            appearance.setVisibleSignature(new Rectangle(100, 100, 200, 200), 1, "signature");

            appearance.setCrypto(privateKey, chain, null, PdfSignatureAppearance.SELF_SIGNED);

            stamper.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Remember to handle exceptions, manage resources properly, and customize the signature appearance as needed. This code snippet provides a basic structure for adding a digital signature at runtime to a PDF file using a digital certificate stored in a ".pfx" file.

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