iTextSharp.text.pdf.PdfEncryption.ComputeOwnerKey C# (CSharp) Метод

        private byte[] ComputeOwnerKey(byte[] userPad, byte[] ownerPad)
        {
            byte[] ownerKey = new byte[32];

            byte[] digest = DigestAlgorithms.Digest("MD5", ownerPad);
            if (revision == STANDARD_ENCRYPTION_128 || revision == AES_128) {
            byte[] mkey = new byte[keyLength / 8];
            // only use for the input as many bit as the key consists of
            for (int k = 0; k < 50; ++k)
                Array.Copy(DigestAlgorithms.Digest("MD5", digest, 0, mkey.Length), 0, digest, 0, mkey.Length);
            Array.Copy(userPad, 0, ownerKey, 0, 32);
            for (int i = 0; i < 20; ++i) {
                for (int j = 0; j < mkey.Length ; ++j)
                    mkey[j] = (byte)(digest[j] ^ i);
                rc4.PrepareARCFOURKey(mkey);
                rc4.EncryptARCFOUR(ownerKey);
            }
            }
            else {
            rc4.PrepareARCFOURKey(digest, 0, 5);
            rc4.EncryptARCFOUR(userPad, ownerKey);
            }

            return ownerKey;
        }