> For the complete documentation index, see [llms.txt](https://docs.verifone.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.verifone.com/adk-os-platform/readme/system-overview-and-architecture.md). # System overview and architecture Understand the VOS3 platform model, supported hardware, processors, and core system services. VOS3 runs on a dual-processor platform. The application processor handles UX, networking, and application runtime. The secure processor handles protected input, card interfaces, and security functions. ## What this page covers Use this page to understand: * the VOS3 platform model * supported hardware * processor responsibilities * core system services and control panels ## Introduction Verifone Operating System 3 (VOS3) is the next-generation operating system for Verifone point-of-sale devices. It is based on Embedded Linux. It supports the Verifone Application Development Kit (ADK). Many APIs remain familiar to teams migrating from earlier Engage platforms. ## Hardware and supported devices VOS3 runs on the application processor in the device. The application processor drives the display, touch, speaker, and communications interfaces such as Wi-Fi, Bluetooth, cellular, Ethernet, USB, and serial. A secure processor is connected through an internal interconnect. It handles secure touch and keypad input, magnetic stripe, contact chip, contactless chip cards, and secure access modules (SAM). ![](https://3462522456-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FIfFmiYwINerMPYjzrAC6%2Fuploads%2Fgit-blob-06adf3f436341032c184f863a256aabb53493780%2F0%20\(1\)%20\(1\)%20\(1\).png?alt=media) VOS3 support is currently provided for these Verifone products: * P630 pinpad * M425 and M450 multi-lane pinpads * Ux700 AIO and Ux700-ML unattended products Support for additional products is planned. ## Software stack overview The following diagram shows the main software components on the secure processor and application processor. ![](https://3462522456-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FIfFmiYwINerMPYjzrAC6%2Fuploads%2Fgit-blob-dec26555860178861d17aff2b4bb58bf8e26635a%2F1%20\(1\)%20\(1\)%20\(1\).png?alt=media) ## Secure processor The secure processor provides the highest-trust functions in the system. ### Secure processor boot loader The secure processor boot loader loads and authenticates the secure processor firmware. ### Secure processor firmware The secure processor firmware implements: * tamper detection and tamper response * key management for secure Verifone VRK key loading * extended key management for master and session key handling * 3DES, AES, RSA, and ECC operations * PIN entry and sensitive data entry on keypad and touch-only devices * PIN block generation and encryption * magnetic stripe reading * ICC and SAM reading with L1 processing * contactless reading with L1 processing * secure PIN transfer from connected Verifone companion pinpads It also provides additional platform functions such as: * non-PIN keypad prompts * built-in printer support ## Application processor The application processor provides the main runtime environment for applications and system services. ### Application boot loader The application boot loader is part of the secure boot chain. It verifies firmware and application authenticity and integrity during startup. The exact boot loader design depends on the hardware platform. ### Linux kernel The Linux kernel provides the base runtime for system services and applications. Applications use standard system APIs for file I/O, memory management, threading, and related functions. Kernel revisions can differ by product. The exposed Linux APIs are intended to stay stable across supported VOS3 devices. Linux also provides the base isolation model for files, processes, and memory. Direct access to some low-level devices is restricted. Applications use system services when access needs arbitration or protection. ### Radio firmware Separate firmware is required for Wi-Fi, Bluetooth, and cellular chipsets where present. ### System services VOS3 provides system services on top of Linux. These services usually run in the background and expose functionality through API libraries. Core services include: * **Secure Installation Service (INS)** — verifies, authenticates, and installs system and application download packages * **Compromise Detection Daemon (CDD)** — checks system integrity, records tamper state, and controls the 24-hour reboot process * **Communication Daemon (COM)** — manages cellular, Wi-Fi, Ethernet, Bluetooth, USB, and serial communications * **Secure Data Interface (SDI)** — exposes secure processor functions such as card access, EMV processing, PIN entry, crypto, and cardholder data protection * **System Property Service (SYSPROP)** — exposes global system properties * **User Interface Services (UI)** — provide HTML rendering, video playback, printing, and audio support * **System Downloader (DL)** — handles local software download * **Remote Maintenance Agent (VHQ)** — connects the device to Verifone VHQ for remote maintenance * **Secure Processor Connector** — manages the link to the secure processor * **CP Proxy** — provides a connectivity proxy for Verifone CP applications ### System applications and control panels VOS3 also provides system applications and control panels. Key components include: * **Multi-Application Desktop (MAC)** — application launcher, desktop and switcher, status bar, and entry point to control panels * **Communication Control Panel (CCP)** — communication setup and network configuration * **SW Control Panel (SWCP)** — local package download and installation from USB or a connected host * **Security Control Panel (SCP)** — warrantied key loading, customer key loading, and security status * **Logging Control Panel (LCP)** — log level setup, output control, and log transfer * **Power Control Panel** — sleep, reboot, and shutdown actions * **CP Downloader** — local downloader for Verifone CP applications ### Verifone ADK programming APIs The Verifone ADK extends the base Linux APIs with platform-specific functions. These functions are implemented by secure processor firmware and system services. The SDK includes the required headers, libraries, and development tools. ### User applications User applications implement customer-facing and payment functionality on the terminal. They use Linux APIs and Verifone ADK APIs. Applications are typically sandboxed by user and home directory. This model supports multiple installed applications and concurrent execution. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.verifone.com/adk-os-platform/readme/system-overview-and-architecture.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.