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

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

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

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:

Implement (use) custom data encryption class that implements IDataEncryption interface.
Create instance of custom encryption object
Instantiate the QrCodeSearchOptions object and setup DataEncryption value with custom encryption object implementation
Call Search method of Signature class instance and pass QrCodeSearchOptions to it.

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 : IDataEncryption
{
    /// <summary>
    /// Gets or sets non empty key for encryption (at least one character)
    /// </summary>
    public int Key { get; set; }
    /// <summary>
    /// Encode method to encrypt string.
    /// </summary>
    /// <param name="source">Source string to encode.</param>
    /// <returns>Returns enccrypted string</returns>
    public string Encode(string source)
    {
        return Process(source);
    }
    /// <summary>
    /// Decode method to obtain decrypted string.
    /// </summary>
    /// <param name="source">Source string to decode.</param>
    /// <returns>Returns decrypted string</returns>
    public string Decode(string source)
    {
        return Process(source);
    }
    /// <summary>
    /// Using XOR operation get encoded / decoded string
    /// </summary>
    /// <param name="source"></param>
    /// <returns></returns>
    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[index];
            chTmp = (char)(chTmp ^ this.Key);
            dst.Append(chTmp);
        }
        return dst.ToString();
    }
}

Definition of class

This example shows how to define custom class for serialization.

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

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

// instantiating the signature object
using (Signature signature = new Signature("signed.pdf"))
{
    // setup search options
    QrCodeSearchOptions searchOptions = new QrCodeSearchOptions();
    // specify as true to search all pages of a document
    searchOptions.AllPages = true;
    searchOptions.DataEncryption = new CustomXOREncryptionAttribute();
    // search document
    List<QrCodeSignature> signatures = signature.Search<QrCodeSignature>(searchOptions);
    // output signatures
    foreach (QrCodeSignature qrCodeSignature in signatures)
    {
        if (qrCodeSignature != null)
        {
            DocumentSignatureData docSignature = qrCodeSignature.GetData<DocumentSignatureData>();
            if (docSignature != null)
            {
                Console.WriteLine("Found DocumentSignature: #{0} by {1} from {2} DataFactor = {3}", docSignature.ID,
                    docSignature.Author, docSignature.Signed, docSignature.DataFactor.ToString("N2"));
            }
        }
    }
}

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.

Search for embedded and encrypted objects in QR-Code signatures Search for embedded object with custom serialization of QR-Code signatures