> For the complete documentation index, see [llms.txt](https://sandbox-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://sandbox-docs.verifone.com/s-adk-5.1-programmers-guide/readme/system_deployment_and_configuration/pg_system_lifecycle.md).
# System Lifecycle
## Lifecycle overview
## Production and Application Development Modes
Verifone provides system users with following device modes:
* PRODUCTION mode
* APPLICATION DEVELOPMENT mode
Production mode is meant for operational usage of the device. In this mode all security provisions are fully enabled.
Application development (APP-DEV) mode is a special mode to support developers during application development and testing. Refer to the [Device Mode conversion](/s-adk-5.1-programmers-guide/readme/developing_applications/pg_device_mode_conversion.md) chapter to read details about this mode.
{% hint style="info" %}
Conversion to APP-DEV mode is provided by Verifone and converted devices can be ordered separately.
{% endhint %}
A device can be moved out from the field using the CrtReset tool that removes authentication certificates, keys and other customer data from the device. Refer to the [System Tools](/s-adk-5.1-programmers-guide/readme/pg_system_tools.md) to read more details about this tool.
## System Warrantied Keys
The system comes preloaded with a set of warrantied keys as per the following table:
| Warrantied Key | Details | Key Type |
| ---------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------- | ----------------- |
| VRK Key: Verifone Remote Key Loading Key | VRK key is used for encrypt/decrypt of the VRK Payload for RSA and for key agreement of encryption/decryption key of the VRK payload for ECC. | ECC-521 |
| Authentication Key (Authex/ AuthN) | Authenticate the device against external service (e.g. VHQ, custom TMS) | RSA-2048, ECC-521 |
| Pairing Key | Authenticate a connected Verifone Device and establish trust for key exchange between Verifone Devices | RSA-2048, ECC-521 |
| System Signer | Reserved for Verifone private use | ECC-521 |
---
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