Sign documents with encrypted metadata text

GroupDocs.Signature provides ability to secure Metadata signatures with standard or custom encryption. Standard encryption is implemented over class SymmetricEncryption class. Creation of this object expects 3 arguments like encryption algorithm enumeration SymmetricAlgorithmType with one of following values (DES, TripleDES, RC2, Rijndael), string value key and string value salt.

Here are the steps to secure Metadata string values with standard encryption with GroupDocs.Signature:

Create new instance of Signature class and pass source document path or stream as a constructor parameter.
Compose object of SymmetricEncryption class with required algorithm and secure pair key/salt
Create objects of MetadataSignOptions class and setup property MetadataSignOptions.DataEncryption with object of SymmetricEncryption. In this case all added Metadata signatures to options collection will be encrypted.
Alternative way to encrypt only selected Metadata signatures is to setup property MetadataSignature.DataEncryption to each signature that requires to be secured.
Create required collection of MetadataSignature object with proper class for document type (like PdfMetadataSignature, ImageMetadataSignature, PresentationMetadataSignature, SpreadsheetMetadataSignature, WordProcessingMetadataSignature)
Call Sign method of Signature class instance and pass MetadataSignOptions to it.

Implementation of encrypted Metadata signature

This example shows how to sign document with encrypted Metadata signatures over .

using (Signature signature = new Signature("sample.docx"))
{
    // setup key and passphrase
    string key = "1234567890";
    string salt = "1234567890";
    // create data encryption
    IDataEncryption encryption = new SymmetricEncryption(SymmetricAlgorithmType.Rijndael, key, salt);
    // setup options with text of signature
    MetadataSignOptions options = new MetadataSignOptions()
    {

    };
    
    // setup signature metadata - this text will not be encrypted
    WordProcessingMetadataSignature mdAuthor = new WordProcessingMetadataSignature("Author", "Mr.Scherlock Holmes");

    // setup data of document id
    WordProcessingMetadataSignature mdDocId = new WordProcessingMetadataSignature("DocumentId", Guid.NewGuid().ToString());
    // set encryption for separate metadata signatures for this options
    mdDocId.DataEncryption = encryption
    
    // add signatures to options
    options.Signatures.Add(mdAuthor);
    options.Signatures.Add(mdDocId);
    // sign document to file
    signature.Sign("MetadataEncryptedText.docx", options);

}

Implementation of encrypted Metadata signature over MetadataSignOptions encryption

This example shows how to sign document with encrypted Metadata signatures over .

using (Signature signature = new Signature("sample.docx"))
{
    // setup key and passphrase
    string key = "1234567890";
    string salt = "1234567890";
    // create data encryption
    IDataEncryption encryption = new SymmetricEncryption(SymmetricAlgorithmType.Rijndael, key, salt);
    // setup options with text of signature
    MetadataSignOptions options = new MetadataSignOptions()
    {
        // set encryption for all metadata signatures for this options
        // if you need separate encryption use own MetadataSignature.DataEncryption property
        DataEncryption = encryption
    };
    
    // setup signature metadata
    WordProcessingMetadataSignature mdAuthor = new WordProcessingMetadataSignature("Author", "Mr.Scherlock Holmes");
    // setup data of document id
    WordProcessingMetadataSignature mdDocId = new WordProcessingMetadataSignature("DocumentId", Guid.NewGuid().ToString());
    
    // add signatures to options
    options.Signatures.Add(mdAuthor);
    options.Signatures.Add(mdDocId);
    // sign document to file
    signature.Sign("MetadataEncryptedText.docx", 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.

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