Search for embedded object with custom serialization of QR-Code signatures

GroupDocs.Signature provides following abilities to search for embedded data objects in QR-code signatures (QrCodeSignature) that were embedded with custom encryption and serialization 

  • ability to search for embedded custom objects into metadata and decrypt them to original source values
  • ability to search for custom encrypted QR-code signature and decrypt it
  • ability to search for custom serialized QR-code signatures  

Here are the steps to search and decrypt previously encrypted text of QR-Code and decrypt custom object from QR-Code signature with GroupDocs.Signature API:

Implementation of custom data serialization

 This example shows how to specify custom serialization class. This class should be implemented as Attribute and IDataSerializer interface.

/**
 * Creates class that implements IDataSerializer interface
 * It cam support common serialization like JSon or custom data format
 */
public class CustomSerializationAttribute implements IDataSerializer{
 
 
    public <T> T deserialize(String source, Class<T> type)
    {
        return new Gson().fromJson(source, type);
    }
    public String serialize(Object data)
    {
        return new Gson().toJson(data);
    }
 
}

Implementation of custom data encryption

This example shows how to specify custom serialization class. This class could be implemented also as Attribute (optional) to specify as class attribute.

// Define class that implements IDataEncryption interface
// Class could inherits Attribute to use it with class definition
 
public class CustomXOREncryption implements IDataEncryption
{
    /**
     * <p>
     * Gets or sets non empty key for encryption (at least one character)
     * </p>
     */
    public final int getKey(){ return auto_Key; }
    /**
     * <p>
     * Gets or sets non empty key for encryption (at least one character)
     * </p>
     */
    public final void setKey(int value){ auto_Key = value; }
    private int auto_Key;
 
    /**
     * <p>
     * Encode method to encrypt string.
     * </p>
     * @return Returns enccrypted string
     * @param source Source string to encode.
     */
    public final String encode(String source)
    {
        return process(source);
    }
 
    /**
     * <p>
     * Decode method to obtain decrypted string.
     * </p>
     * @return Returns decrypted string
     * @param source Source string to decode.
     */
    public final String decode(String source)
    {
        return process(source);
    }
 
    /**
     * <p>
     * Using XOR operation get encoded / decoded string
     * </p>
     * @return
     * @param source
     */
    private String process(String source)
    {
        StringBuilder src = new StringBuilder(source);
        StringBuilder dst = new StringBuilder(src.length());
        char chTmp;
        for (int index = 0; index < src.length(); ++index)
        {
            chTmp = src.charAt(index);
            chTmp = (char)(chTmp ^ this.getKey());
            dst.append(chTmp);
        }
        return dst.toString();
    }
}

Definition of class

This example shows how to define custom class for serialization.

public static class DocumentSignatureData
{
    public String getID(){ return ID; }
    public void setID(String value){ ID = value; }
    @FormatAttribute(propertyName = "SignID")
    public String ID;
 
 
    public final String getAuthor(){ return Author; }
    public final void setAuthor(String value){ Author = value; }
    @FormatAttribute(propertyName = "SAuth")
    public String Author;
    //JAVA-added public wrapper for internalized property accessor
 
    public final java.util.Date getSigned() {  return Signed; }
    public final void setSigned(java.util.Date value) { Signed = value; }
    @FormatAttribute (propertyName = "SDate",propertyFormat = "yyyy-MM-dd")
    public java.util.Date Signed = new java.util.Date();
 
 
    public final java.math.BigDecimal getDataFactor() { return DataFactor; }
    public final void setDataFactor(java.math.BigDecimal value) { DataFactor = value; }
    @FormatAttribute (propertyName = "SDFact",propertyFormat = "N2")
    public java.math.BigDecimal DataFactor = new java.math.BigDecimal(0.01);
}

Search for embedded custom objects in QR-code signatures

This example shows how to decrypt previously embedded encrypted custom objects into QrCodeSignature contains method getData to retrieve object

Signature signature = new Signature("QRCodeCustomSerializationObject.pdf");
// create data encryption
IDataEncryption encryption = new CustomXOREncryption();
 
QrCodeSearchOptions options = new QrCodeSearchOptions();
 
// specify special pages to search on
options.setAllPages(true);
options.setDataEncryption(encryption);
 
 
// search for signatures in document
List<QrCodeSignature> signatures = signature.search(QrCodeSignature.class,options);
System.out.print("\nSource document contains following signatures:");
for (QrCodeSignature qrCodeSignature : signatures)
{
    System.out.print("QRCode signature found at page "+qrCodeSignature.getPageNumber()+" with type "+ qrCodeSignature.getEncodeType());
    DocumentSignatureData documentSignatureData = qrCodeSignature.getData(DocumentSignatureData.class);
    if (documentSignatureData != null)
    {
        System.out.print("QRCode signature has DocumentSignatureData object:\n ID = " + documentSignatureData.getID() + ", Author = " + documentSignatureData.getAuthor() + ", Signed = " + documentSignatureData.getSigned() + ", DataFactor "+documentSignatureData.getDataFactor());
    }
}

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.

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