iTextSharp.text.pdf.PdfPublicKeySecurityHandler.CreateDERForRecipient C# (CSharp) Метод

        private Asn1Object CreateDERForRecipient(byte[] inp, X509Certificate cert)
        {
            String s = "1.2.840.113549.3.2";

            byte[] outp = new byte[100];
            DerObjectIdentifier derob = new DerObjectIdentifier(s);
            byte[] keyp = IVGenerator.GetIV(16);
            IBufferedCipher cf = CipherUtilities.GetCipher(derob);
            KeyParameter kp = new KeyParameter(keyp);
            byte[] iv = IVGenerator.GetIV(cf.GetBlockSize());
            ParametersWithIV piv = new ParametersWithIV(kp, iv);
            cf.Init(true, piv);
            int len = cf.DoFinal(inp, outp, 0);

            byte[] abyte1 = new byte[len];
            System.Array.Copy(outp, 0, abyte1, 0, len);
            DerOctetString deroctetstring = new DerOctetString(abyte1);
            KeyTransRecipientInfo keytransrecipientinfo = ComputeRecipientInfo(cert, keyp);
            DerSet derset = new DerSet(new RecipientInfo(keytransrecipientinfo));
            Asn1EncodableVector ev = new Asn1EncodableVector();
            ev.Add(new DerInteger(58));
            ev.Add(new DerOctetString(iv));
            DerSequence seq = new DerSequence(ev);
            AlgorithmIdentifier algorithmidentifier = new AlgorithmIdentifier(derob, seq);
            EncryptedContentInfo encryptedcontentinfo =
                new EncryptedContentInfo(PkcsObjectIdentifiers.Data, algorithmidentifier, deroctetstring);
            EnvelopedData env = new EnvelopedData(null, derset, encryptedcontentinfo, null);
            Org.BouncyCastle.Asn1.Cms.ContentInfo contentinfo =
                new Org.BouncyCastle.Asn1.Cms.ContentInfo(PkcsObjectIdentifiers.EnvelopedData, env);
            return contentinfo.ToAsn1Object();
        }