Sign documents with QR-code embedded object

GroupDocs.Signature provides ability to embed into QR-code signature custom objects. This feature is implemented over object serialization to string and further encryption. By default library uses json format serialization and symmetric encryption, the class SymmetricEncryption class. Creation of this encryption expects 3 arguments like encryption algorithm enumeration SymmetricAlgorithmTypewith one of following values (DES, TripleDES, RC2, Rijndael), string value key and string value salt.

Here are the steps to embed into QR-code text with standard encryption with GroupDocs.Signature:

  • Implement if needed custom data serialization class that implement IDataSerializer interface. By default GroupDocs.Signature uses embedded json format serialization but allows user to customize it.
  • Implement if needed custom data encryption class that implements IDataEncryption interface. By default GroupDocs.Signature has several encryption implementation you can use but allows user to customize it.
  • Implement class with properties and specify if needed class attributes (like custom serialization attribute, custom encryption attribute), specify attributes for properties like FormatAttribute  to specify serialization name and display format, same as SkipSerializationAttribute to mark property of class as not serialize
  • Create new instance of  Signature class and pass source document path as a constructor parameter.
  • Create one or several objects of QrCodeSignOptions object with Data value
  • Instantiate the  QrCodeSignOptions  object according to your requirements and custom object to Data property.
  • Call Sign method of  Signature  class instance and pass QrCodeSignOptions to it.

Definition of class

This example shows how to define custom class with serialization and encryption properties and setup Format attributes for properties.

public class DocumentSignatureData
    public string ID { get; set; }
    public string Author { get; set; }
    [Format("SDate", "yyyy-MM-dd")]
    public DateTime Signed { get; set; }
    [Format("SDFact", "N2")]
    public decimal DataFactor { get; set; }
    public string Comments { get; set; }

Implementation of embedding custom object into QR-code signature

This example shows how to embed custom object into QR-code signature.

using (Signature signature = new Signature("sample.pdf"))
    // setup key and passphrase
    string key = "1234567890";
    string salt = "1234567890";
    // create data encryption
    IDataEncryption encryption = new SymmetricEncryption(SymmetricAlgorithmType.Rijndael, key, salt);
    // create custom object
    DocumentSignatureData documentSignatureData = new DocumentSignatureData()
        ID = Guid.NewGuid().ToString(),
        Author = Environment.UserName,
        Signed = DateTime.Now,
        DataFactor = 11.22M
    // setup QR-Code options
    QrCodeSignOptions options = new QrCodeSignOptions()
        // set custom object to serialize to QR Code
        Data = documentSignatureData,
        // QR-code type
        EncodeType = QrCodeTypes.QR,
        // specify serialization encryption
        DataEncryption = encryption,
        // locate and aligh signature
        Height = 100,
        Width = 100,
        VerticalAlignment = VerticalAlignment.Bottom,
        HorizontalAlignment = HorizontalAlignment.Right,
        Margin = new Padding() { Right = 10, Bottom = 10 }
    // sign document to file
    signature.Sign("QrCodeEncryptedObject.pdf", options);

More resources

GitHub Examples

You may easily run the code above and see the feature in action in our GitHub examples:

Free Online App

Along with full-featured .NET library we provide simple, but powerful free Apps.

You are welcome to eSign PDF, Word, Excel, PowerPoint documents with free to use online GroupDocs Signature App.