Sec-ALG: An Open-source Application Layer Gateway for Secure Access to Private Networks

Maria Riaz*, Juha-Matti Tilli, Raimo Kantola

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

1 Citation (Scopus)
64 Downloads (Pure)


Middleboxes such as Network Address Translators (NATs), proxy servers or Application Layer Gateways (ALGs) provide remote access to end-hosts in the private address space. The middleboxes offer proprietary solutions and encrypted traffic poses a challenge when middleboxes employ packet payload inspection techniques for connection establishment. Session key sharing and decryption followed by re-encryption of the traffic, for correctly routing to the private host, increases the connection latency and also poses a higher threat in case of traffic interception by a malicious third-party.In this paper, we present a novel open-source ALG, called Sec-ALG, for providing secure end-to-end communication to the web servers situated in the private address space. Sec-ALG relies on the technique of light Deep Packet Inspection (DPI) for protocol detection and session establishment using a novel parser-lexer generator called YaLe. The proposed approach offers increased security by maintaining end-to-end encryption for an HTTPS connection. Our experimental analysis demonstrates that Sec-ALG reduces the HTTPS connection latency in comparison to the NGINX reverse proxy using a 24-core host machine. Moreover, Sec-ALG handles requests at a three-fold increased rate than NGINX proxy when tested with 100 concurrent connections. The ALG can be used either as a standalone solution or a component of the Realm Gateway, that is a generic interworking solution between public and private networks. The presented work is part of an extensive ongoing research at Aalto University focusing on embedding policy based trust into the network.

Original languageEnglish
Title of host publicationProceedings of the 29th International Conference on Computer Communications and Networks, ICCCN 2020
Number of pages11
ISBN (Electronic)9781728166070
Publication statusPublished - Aug 2020
MoE publication typeA4 Article in a conference publication
EventInternational Conference on Computer Communications and Networks - Honolulu, United States
Duration: 3 Aug 20206 Aug 2020
Conference number: 29

Publication series

NameProceedings : International Conference on Computer Communications and Networks
ISSN (Print)1095-2055


ConferenceInternational Conference on Computer Communications and Networks
Abbreviated titleICCCN
Country/TerritoryUnited States


  • Middleboxes
  • Protocols
  • Logic gates
  • Cryptography
  • Web servers


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