public CmsSignedDataParser(
     CmsTypedStream signedContent,
     byte[]                  sigBlock)
     : this(signedContent, new MemoryStream(sigBlock, false))
 {
 }
        /**
         * base constructor
         *
         * @param signedContent the content that was signed.
         * @param sigData the signature object.
         */
        public CmsSignedDataParser(
            CmsTypedStream signedContent,
            Stream sigData)
            : base(sigData)
        {
            try
            {
                this._signedContent = signedContent;
                this._signedData    = SignedDataParser.GetInstance(this.contentInfo.GetContent(Asn1Tags.Sequence));
                this._digests       = Platform.CreateHashtable();
                this._digestOids    = new HashSet();

                Asn1SetParser    digAlgs = _signedData.GetDigestAlgorithms();
                IAsn1Convertible o;

                while ((o = digAlgs.ReadObject()) != null)
                {
                    AlgorithmIdentifier id = AlgorithmIdentifier.GetInstance(o.ToAsn1Object());

                    try
                    {
                        string digestOid  = id.Algorithm.Id;
                        string digestName = Helper.GetDigestAlgName(digestOid);

                        if (!this._digests.Contains(digestName))
                        {
                            this._digests[digestName] = Helper.GetDigestInstance(digestName);
                            this._digestOids.Add(digestOid);
                        }
                    }
                    catch (SecurityUtilityException)
                    {
                        // TODO Should do something other than ignore it
                    }
                }

                //
                // If the message is simply a certificate chain message GetContent() may return null.
                //
                ContentInfoParser     cont = _signedData.GetEncapContentInfo();
                Asn1OctetStringParser octs = (Asn1OctetStringParser)
                                             cont.GetContent(Asn1Tags.OctetString);

                if (octs != null)
                {
                    CmsTypedStream ctStr = new CmsTypedStream(
                        cont.ContentType.Id, octs.GetOctetStream());

                    if (_signedContent == null)
                    {
                        this._signedContent = ctStr;
                    }
                    else
                    {
                        //
                        // content passed in, need to read past empty encapsulated content info object if present
                        //
                        ctStr.Drain();
                    }
                }

                _signedContentType = _signedContent == null
                                        ?       cont.ContentType
                                        :       new DerObjectIdentifier(_signedContent.ContentType);
            }
            catch (IOException e)
            {
                throw new CmsException("io exception: " + e.Message, e);
            }
        }