> For the complete documentation index, see [llms.txt](https://docs.arcan.finance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.arcan.finance/litepaper.md). # Litepaper Arcan lets a public chain hold confidential assets. The asset still moves. The amount stays ciphertext from the user to the contract and back. The encryption is fully homomorphic. A contract can add, subtract, multiply, and compare without decrypting. The result is a new ciphertext. Anyone can recompute that result from the recorded operation and get the same handle. ## Why the chain does not run the math FHE is heavy. Robinhood does not execute it. The contract runs in symbolic mode: it checks the call, updates handles, and records the operation. A coprocessor network performs the encrypted arithmetic and commits the result. The host chain keeps the handle, not the number. ## What a developer writes A confidential contract is ordinary Solidity plus the Arcan FHE library. * A balance is an `euint64`, not a `uint256`. * An input from a user arrives as an `externalEuint64` plus an input proof. `FHE.fromExternal` turns that into a handle the contract can use. * Transfers use `FHE.add` and `FHE.sub`. * Conditions use `FHE.select`, which returns one sealed value or the other. * `FHE.allow` writes the access list: holder, auditor, contract, or anyone else who may later open that handle. ## What a user sees Addresses are public. The from and to of a transfer are public. The value is `****` unless the account is on the access list for that handle. A read such as `confidentialBalanceOf` returns the handle. It does not return the amount to the chain, to an indexer, or to a stranger. ## Composition One public encryption key is used across contracts. A sealed output from one contract can be an input to another, as long as the access list grants the next contract the handle. That is how a token, a payroll contract, and a wrapper can sit on the same ciphertext. ## What this system is for * Confidential tokens that mirror ERC-20 calls with sealed amounts. * Payroll that pays without publishing the salary. * Trades where the position size stays off the public book. * Distributions that split a pool without listing each share in the clear. The protocol does not put the plaintext on Robinhood in order to compute it. Opening a value is a separate step, and only for a name on the list. --- # 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 following URL with the `ask` and `goal` query parameters: ``` GET https://docs.arcan.finance/litepaper.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `build a script that syncs our docs to a CMS` lets GitBook tailor the answer to that use case. 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.