> For the complete documentation index, see [llms.txt](https://docs.atsign.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.atsign.com/atsign-platform/core.md).

# Atsign Platform Overview

An overview of Atsign's core pillars of technology

## Overview

Atsign Platform allows people, entities and things to communicate privately and securely without having to know about the intricacies of the underlying IP network. The Atsign Protocol is the application protocol used to communicate, and Atsigns are the addresses on the protocol. All cryptographic keys are cut at the edge by the Atsign owner, meaning only the receiving and sending Atsigns see data in the clear.

Atsign Platform can be used to send data synchronously or asynchronously, and can be used as a data plane, or a control plane, or both, simultaneously at Internet scale.

<figure><img src="https://1631869959-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FpQPWQHMckXtXYemavYhN%2Fuploads%2FigUMWoclnj8vd6KJYxkK%2Fdark_mode.png?alt=media&amp;token=1887d500-d514-4b3e-9279-bc4ec6341fc1" alt="Atsign platform visual showing the 5 pillars: SDKs, atDirectory, Atsign protocol, Atsign and atServer"><figcaption><p>Atsign Platform composition (dark mode)</p></figcaption></figure>

<figure><img src="https://1631869959-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FpQPWQHMckXtXYemavYhN%2Fuploads%2FKmxvG2bIMhuOGmyG5K74%2Flight_mode.png?alt=media&amp;token=4917c117-ec5d-4768-bff9-870f75b66765" alt="Atsign platform composition, light mode"><figcaption><p>Atsign Platform composition (light mode)</p></figcaption></figure>

<details>

<summary>Relationships</summary>

Every **atServer** is associated with *one* **Atsign**, and each atServer stores *many* **atRecords.**

When provided an **Atsign**, the **atDirectory** returns a *DNS address* and *port number* for its **atServer.**

The **Atsign Protocol** is the *application layer protocol* used to communicate with an **atServer.**

</details>

## Core Components

The Atsign Platform consists of multiple components that work together:

<table data-view="cards"><thead><tr><th></th><th></th><th data-type="content-ref"></th></tr></thead><tbody><tr><td>Atsign</td><td>The identity for people, entities, and things.</td><td><a href="/atsign-platform/atsign/atsign.md">Atsign</a></td></tr><tr><td>atDirectory</td><td>Address book for Atsigns (like DNS)</td><td><a href="/atsign-platform/atdirectory.md">atDirectory</a></td></tr><tr><td>atServer</td><td>An Atsign's personal data  service for sync/async communications</td><td><a href="/atsign-platform/atserver.md">atServer</a></td></tr><tr><td>SDKs</td><td>Toolkits to help developers build applications on the platform</td><td><a href="/atsign-platform/sdks.md">SDKs</a></td></tr><tr><td>Atsign Protocol</td><td>Layer 7 protocol that connects everything together</td><td><a href="/atsign-platform/atsign-protocol.md">Atsign Protocol</a></td></tr></tbody></table>