> For the complete documentation index, see [llms.txt](https://shinkalabs.gitbook.io/hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shinkalabs.gitbook.io/hub/andromeda/concepts/fhe.md).

# Confidential computing (FHE)

Andromeda exposes Encrypt's fully homomorphic encryption (FHE) layer on Solana. FHE lets a program compute over data that stays encrypted the whole time: you submit ciphertexts, an evaluator runs an arithmetic graph on them, and the result comes back still encrypted, decryptable only by whoever holds the right key.

{% hint style="warning" %}
This runs against the Encrypt pre-alpha network. There is no real confidentiality guarantee yet. Do not describe these flows as private to end users.
{% endhint %}

## The building blocks

You will see these terms across the [Encrypt FHE surface](/hub/andromeda/guides/encrypt-fhe.md):

* **Ciphertext.** An encrypted value, stored in a Solana account. Create one from a plaintext input, read one back, or look it up by account.
* **Graph.** A pipeline of FHE operations (additions, comparisons, selects, and so on) applied to ciphertext inputs. Graphs can be executed ad hoc, registered once and re-executed by reference, or committed.
* **DSL.** A small set of typed operations you can compose into a graph without hand-building bytecode. `GET /v1/dsl/types` lists the available types; `POST /v1/dsl/op/prepare` builds an operation.
* **Decryption request.** Asks the network to decrypt a ciphertext for an authorised party; you then poll for the result.
* **NEK (network encryption key).** The public key the network uses for this deployment. `GET /v1/nek/current` returns it.
* **Authority and fees.** Graph execution is paid from a fee account; authorities (the keys allowed to act on a confidential account) are managed with their own endpoints.

## Where it fits

There are two ways FHE shows up:

1. **Directly**, through the Encrypt surface, when you want confidential primitives in your own application. See [The Encrypt FHE surface](/hub/andromeda/guides/encrypt-fhe.md).
2. **As a gate**, through [Confidential workflows](/hub/andromeda/guides/confidential-workflows.md): an FHE evaluation produces a decision, the decision is signed by a key held in a KMS, and the on-chain `fhe-gated` policy validates that decision before releasing an Ika signature. This is how you make a signature conditional on logic that ran over encrypted inputs.

## Custody-free, like the rest

Every mutating FHE call is a `.../prepare` endpoint that returns an unsigned transaction. You sign it client-side and submit it via `POST /v1/graph/submit` (or `POST /v1/private-tx/submit`). Andromeda never signs your transactions for the Encrypt surface. See [Custody-free model](/hub/andromeda/concepts/custody-free.md).


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