# 2.1 Core Features The HNDL smart contract offers the following core features: **Sub-Handle Registration** Users can mint sub-handles under parent handles with fees based on character count. Permissions are granted by the parent handle owner, and 100% of the sub-handle registration fees go towards the parent handle owner. **Sub-Handle Permission** Parent handle owners possess the authority to enable or disable sub-handle minting for their parent handle, thereby permitting or prohibiting other users from minting sub-handles under their parent handle. **Renewals** Users retain the ability to renew the registration of their own or other users' handles for additional years autonomously, without necessitating permission. **Renewal Halving** At intervals of every 8 years following the deployment of the smart contract, the fees for handles undergo a halving process to sustain their resilience against inflation.\ \ **Public** **Data Storage** Users have the capability to store public data on their handles, including zone files, images, videos, text-based information, JSON files, and other formats. **Sign In With HNDL (SIWH)** Users have the ability to sign in to applications using their handle while maintaining ownership of their public and private data.\ \ **App-specific Data Storage** Users are empowered to store both public and private data customized for specific applications, guaranteeing that only they and the designated app can access and retrieve the stored information. For private data, encryption is applied, allowing another smart contract to read and confirm certain information without the app needing access to the full details. **Token Bound Accounts (ERC-6551)** Handles will be linked to their respective Rootstock and Bitcoin addresses, serving as autonomous smart contract wallets. This arrangement enables users to own ERC and Bitcoin Layer 1 assets securely. --- # Agent Instructions: 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: ``` GET https://studybitcoin.gitbook.io/hndl-bitcoin-handle-naming-system/2.1-core-features.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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.