Signal P Server

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Pang Murdock

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Aug 3, 2024, 4:20:13 PM8/3/24
to riagrapwencha

Signal seems to be the ONE that really cares and provides end to end encryption for the sent data. What is more, application code can be found on github under the Signal organization and was independently audited. This service has around 50 million users and even other IMs leverage its protocol!

Signal protocol can be used for end to end encryption of all messages, but also for video calls. It has passed security audits. An interesting fact is that WhatsApp, Facebook Messenger, and Skype actually decided to use Signal Protocol! However, in most cases they use it with encryption disabled, leaving it enabled only for specific private conversations.

In this article, I will focus on the Signal Server. This is the main part of backend architecture providing REST API and WebSockets, being responsible for passing messages to appropriate users and storing them in the database. Keep in mind that it is not the only piece of the system.

Redis is known mostly as a simple key value store. It offers clustering capabilities and is available among providers of cloud offerings. At Signal, you can notice usage of other, more advanced features. The Pub/Sub feature, which, as the name suggests, is the simple Publish Subscribe messaging model, is a critical piece of Signal architecture. When the Signal client opens a websocket connection, it is stored in a special map keyed by the device identifier. When a new message is sent and the device is online, then it is added to redis. Proper pub/sub subscription reads it and checks if the special map contains the websocket connection for the given device. If yes, the message is delivered, otherwise it is ignored. Such scenario handles situations in which there is more than 1 active server (High Availability!).

This script is called for every message that needs to be queued because the device was offline. Later another worker executes different scripts to fetch the set values in order to store them in DynamoDB asynchronously.

Signal REST endpoints include protection against too many requests. The source code includes Rate Limiters mechanisms, which allows to limit e.g. the number of endpoint executions per given message sender. Guess what? This mechanism is also based on Redis.

This code leveraged PostgreSQL Rules mechanism. On every insert to messages table (on every new message), the oldest messages were deleted. Signal kept in the database only 1000 latest messages per-destination. Why? Probably to be even more secure and private. Theoretically, we can assume that a 1000 messages buffer is enough to deliver messages to proper devices. Currently, the DynamoDB based version leverages 7 day TTL.

I am trying to start my custom TextSecure (Signal) server. I want to use it for all functions that Signal has (both SMS and telephony). I believe that I also need redphone server to run telephony. I've found github repos for TextSecure server only -Server but no repos for redphone server.

Twilio - for sms broadcasting(for registration in TextServer).
AWS - for documents in TextSecure.
Google developer - for push notifications.
Apple Developer - for push notifications(i didn't reg this one because i did hack Push server).

With Maven install: Dropwizard-simpleauth, WebSocket-Resources.
With Maven compile PushServer and start it with your settings (redis, auth, gcm, apn).
With Maven compile TextServer with -DskipTests key.
After that you can use your own TextServer but without RedPhone. The RedPhone repo was deleted from github.

The SignalP 5.0 server predicts the presence of signal peptides and the location of their cleavage sites in proteins from Archaea, Gram-positive Bacteria, Gram-negative Bacteria and Eukarya. In Bacteria and Archaea, SignalP 5.0 can discriminate between three types of signal peptides:

  • Sec/SPI: "standard" secretory signal peptides transported by the Sec translocon and cleaved by Signal Peptidase I (Lep)
  • Sec/SPII: lipoprotein signal peptides transported by the Sec translocon and cleaved by Signal Peptidase II (Lsp)
  • Tat/SPI: Tat signal peptides transported by the Tat translocon and cleaved by Signal Peptidase I (Lep)
SignalP 5.0 is based on a deep convolutional and recurrent neural network architecture including a conditional random field.

History paper Click here to read "A Brief History of Protein Sorting Prediction", The Protein Journal, 2019

DeepLoc Remember, the presence or absence of a signal peptide is not the whole story about the localization of a protein! If you want to find out more about the sorting of your eukaryotic proteins, try the protein subcellular localization predictor.

Behind the paper Check out the blog post about the SignalP 5.0 publication.

NOTE:This is not the newest version of SignalP. To use the current version, please go tothe main SignalP site! Submission Instructions Data Article abstract FAQ Version history Portable Downloads Submit data Sequence submission: paste the sequence(s) and/or upload a local file

WebRTC is HTML5 compatible and it allows you to add real-time communications to your apps to directly communicate between browsers and devices. You can do that without any plugins. It is supported by all major browsers including Safari, Google Chrome, Firefox, and Opera.

WebRTC signaling is a process of setting up, controlling, and terminating a communication session between peers. In order for two peers to begin connecting to one another, three types of information must be exchanged:

A WebRTC signaling server is a server that manages the connections between peers. It is just used for signaling. It helps with enabling one peer to find another in the network, negotiating the connection itself, resetting the connection if needed, and closing it down.

All peers send notifications to the server, they are connected, and the server forwards them to the peer. Notification requests can be done over WebSockets or HTTP protocols such as REST for sending and long polling for receiving. Both of these ways need extra effort or power to receive notification messages. For example, WebSocket needs to be alive and it cannot be used on demand or long polling needs to make an HTTP request a lot of time in a short period which consumes bandwidth.

The WebRTC signaling server in the diagram helps two peers find and connect to each other. Both peers are linked to that WebRTC signaling server. You may also be connecting in this way while video chatting with your spouse or making some banking works using video communication with your bank.

The communication between A and the WebRTC signaling server is called the offer-answer mechanism, which is part of WebRTC. These messages are SDP messages, not WebRTC. What happens here is that WebRTC creates SDP blobs. These are bits of messages that the peer needs to signal to the other peer in order to connect to a session. It can be done using a WebRTC signaling server.

Long-polling: Web applications, which are using live content, must get events to refresh their state. Unfortunately, servers without browser requests or WebSocket connections cannot update web pages. Long polling which is a Comet like mechanism makes requests to the server in an interval to get events.

HTTP Streaming: The streaming mechanism is a kind of long polling that keeps the connection open indefinitely. Even if an event is transmitted to the client, the connection will not be closed. While this mechanism solves some issues of long polling, it has its own issues. HTTP streaming will not work with some network intermediaries such as some proxies or gateways because intermediaries cache the answer before sending it to the client. In addition, client buffering and framing techniques can be listed as other issues of it.

Connecting peers and starting communication may sound easy. The internet we use does not allow us to connect with peers as easily as we imagined. To establish this connection and communication, we need to go through firewalls and NAT devices.

WebRTC Signaling uses a protocol known as ICE which collects, exchanges, and then attempts to connect a session using ICE candidates. ICE candidates are potential addresses that can get peers to connect with each other. With three methods, ICE can calculate the fastest and easiest NAT traversal route for a packet to reach its destination peer.

STUN servers are the most used method in WebRTC signaling. In short, it works like this. A STUN server checks the IP address and port for incoming requests and then sends that address to the peer in response. This allows the application to present a publicly accessible address and then forward it via the signaling mechanism to another WebRTC peer.

The last method used by ICE is a TURN relay server. TURN servers are used to stream audio, video, and other real-time data between peers. It does not share signal information as it enables real-time data exchange between peers. TURN servers have public addresses, so peers can connect to them even if they are behind NATs and firewalls.

We got detailed information about signaling and the WebRTC signaling servers. As we mentioned at the beginning of the blog post, WebRTC is not only used for peer-to-peer connections. In N2N scenarios, more than a WebRTC signaling server is needed. One of WebRTC servers is a WebRTC media server.

In some N2N scenarios, 1 person can broadcast to more than one person, or multiple people can broadcast to multiple people. You can think of examples such as webinars you attend, and social media live streams.

Ant Media has been serving more than 1525 customers in 120+ countries all around the world. Customers from different segments such as education, live auctions, radio and TV broadcasts, service providers, government agencies, and gaming companies enhance their business by using Ant Media Server and benefiting from its capabilities.

Signal Server Technology is simply a method of interfacing real world signals into a network environment. The resulting system allows for plant-wide system control and can be custom configured for each customer's specific needs. Since the design can support multiple controllers added to the network at any point in time, the final system offers the customer unlimited future expandability.

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