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Encrypt document with agile encryption handler

To encrypt OpenXML (Office Open XML, OOXML) document using agile encryption handler

1. load the document into an instance of TElOfficeOpenXMLDocument class
2. if the document is encryptable, create an instance of TElOfficeOpenXMLAgileEncryptionHandler class
3. set handler parameters (see below)
4. assign this encryption handler to TElOfficeDocument.EncryptionHandler property
5. call TElOfficeBinaryDocument.EncryptTo() method to encrypt and save the document to a stream.

To specify the password to use with the agile encryption handler you need to call AddPasswordKeyEncryptor() method, which creates TElOfficeOpenXMLPasswordKeyEncryptor object and initializes it with the password, passed in the method's parameter. MS Office supports just one password encryptor per handler. You can set encryption algorithm via CipherAlgorithm property of the handler. Agile encryption handler supports 128- , 192-, 256-bit AES as well as RC2, RC4, DES, Triple DES encryption algorithms.

C#:

void EncryptOpenXMLAgile(string sourceFilename, string destFilename, string password)
{
    TElOfficeDocument Document = new TElOfficeDocument();
    TElOfficeOpenXMLAgileEncryptionHandler AgileEncryptionHandler = new TElOfficeOpenXMLAgileEncryptionHandler();
    try
    {
        Document.Open(sourceFilename);
        if ((Document.DocumentFormat != TSBOfficeDocumentFormat.OpenXML) && !Document.Encryptable)
            throw new Exception("Cannot encrypt OpenXML document using Agile encryption handler");

        AgileEncryptionHandler.CipherAlgorithm = SBConstants.Unit.SB_ALGORITHM_CNT_AES128;
        AgileEncryptionHandler.HashAlgorithm = SBConstants.Unit.SB_ALGORITHM_DGST_SHA1;
        int k = AgileEncryptionHandler.AddPasswordKeyEncryptor(password);
        // below are default settings of TElOfficeOpenXMLPasswordKeyEncryptor class
        TElOfficeOpenXMLPasswordKeyEncryptor PasswordKeyEncryptor = (TElOfficeOpenXMLPasswordKeyEncryptor)AgileEncryptionHandler.get_KeyEncryptors(k);

        PasswordKeyEncryptor.CipherAlgorithm = SBConstants.Unit.SB_ALGORITHM_CNT_AES128;
        PasswordKeyEncryptor.HashAlgorithm = SBConstants.Unit.SB_ALGORITHM_DGST_SHA1;
        PasswordKeyEncryptor.SpinCount = 100000;
        PasswordKeyEncryptor.SaltSize = 16;

        Document.EncryptionHandler = AgileEncryptionHandler;

        using (FileStream f = new FileStream(destFilename, FileMode.CreateNew))
        {
            Document.EncryptTo(f);
        }
    }
    finally
    {
        Document.Dispose();
        AgileEncryptionHandler.Dispose();
    }
}

Delphi:

procedure EncryptOpenXMLAgile(const SourceFilename, DestFilename, Password : string);
var
  Document : TElOfficeDocument;
  AgileEncryptionHandler : TElOfficeOpenXMLAgileEncryptionHandler;
  F : TFileStream;
  k : Integer;
begin
  Document := TElOfficeDocument.Create(nil);
  AgileEncryptionHandler := TElOfficeOpenXMLAgileEncryptionHandler.Create(nil);
  try
    Document.Open(SourceFilename);
    if (Document.DocumentFormat <> dfOpenXML) and not Document.Encryptable then
      raise Exception.Create('Cannot encrypt OpenXML document using Agile encryption handler');

    AgileEncryptionHandler.CipherAlgorithm := SB_ALGORITHM_CNT_AES128;
    AgileEncryptionHandler.HashAlgorithm := SB_ALGORITHM_DGST_SHA1;
    k := AgileEncryptionHandler.AddPasswordKeyEncryptor(Password);
    // below are default settings of TElOfficeOpenXMLPasswordKeyEncryptor class
    with TElOfficeOpenXMLPasswordKeyEncryptor(AgileEncryptionHandler.KeyEncryptors[k]) do
    begin
      CipherAlgorithm := SB_ALGORITHM_CNT_AES128;
      HashAlgorithm := SB_ALGORITHM_DGST_SHA1;
      SpinCount := 100000;
      SaltSize := 16;
    end;

    Document.EncryptionHandler := AgileEncryptionHandler;

    F := TFileStream.Create(DestFilename, fmCreate or fmShareDenyWrite);
    try
      Document.EncryptTo(F);
    finally
      FreeAndNil(F);
    end;
  finally
    FreeAndNil(Document);
    FreeAndNil(AgileEncryptionHandler);
  end;
end;

How To articles about MS Office OpenXML documents

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