---
name: auth-signers
description: NostrSigner in Amethyst: NostrSignerInternal (local key), NostrSignerRemote (NIP-46 bunker), NostrSignerExternal (NIP-55 Android app). Use when signing/encrypting, adding a signer kind, login flows, or debugging sign timeouts.
---

# Signers

Every signed event and every NIP-04/NIP-44 operation goes through a `NostrSigner`. Feature
code never knows which of the three kinds the user has.

## The contract (all `suspend`)

`quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip01Core/signers/NostrSigner.kt`:

```kotlin
abstract class NostrSigner(pubKey: HexKey) {
    open val pubKey: HexKey                       // open: NIP-46 resolves it from the bunker
    abstract fun isWriteable(): Boolean
    suspend fun <T : Event> sign(ev: EventTemplate<T>): T
    abstract suspend fun <T : Event> sign(createdAt: Long, kind: Int, tags: Array<Array<String>>, content: String): T
    abstract suspend fun nip04Encrypt(plaintext: String, toPublicKey: HexKey): String
    abstract suspend fun nip04Decrypt(ciphertext: String, fromPublicKey: HexKey): String
    abstract suspend fun nip44Encrypt(plaintext: String, toPublicKey: HexKey): String
    abstract suspend fun nip44Decrypt(ciphertext: String, fromPublicKey: HexKey): String
    abstract suspend fun decryptZapEvent(event: ZapRequestEvent): PrivateZapEvent
    abstract suspend fun deriveKey(nonce: HexKey): HexKey
    abstract suspend fun signPsbt(psbtHex: String): String   // NIP-BC; may throw UnsupportedMethodException
    abstract fun hasForegroundSupport(): Boolean
    suspend fun decrypt(encryptedContent: String, fromPublicKey: HexKey): String   // picks NIP-04 vs NIP-44
}
```

Failures are thrown as `SignerExceptions` (`nip01Core/signers/SignerExceptions.kt`):
`ReadOnlyException`, `UnauthorizedDecryptionException`, `NothingToDecrypt`,
`AutomaticallyUnauthorizedException`, `ManuallyUnauthorizedException`, `TimedOutException`,
`CouldNotPerformException`, `RunningOnBackgroundWithoutAutomaticPermissionException`,
`SignerNotFoundException`, `UnsupportedMethodException`. Same folder: `NostrSignerSync`
(blocking, for tests/scripts), `EventTemplate.kt`, `caches/` (`DecryptCache`).

## The three signers

| Signer | File | Notes |
|---|---|---|
| `NostrSignerInternal` | `quartz/.../nip01Core/signers/NostrSignerInternal.kt` | key in process memory; created/imported accounts |
| `NostrSignerRemote` | `quartz/.../nip46RemoteSigner/signer/NostrSignerRemote.kt` | NIP-46 bunker over kind 24133; `references/nip46-remote-signer.md` |
| `NostrSignerExternal` | `quartz/src/androidMain/.../nip55AndroidSigner/client/NostrSignerExternal.kt` | NIP-55 app (Amber…) via intents + content provider; Android only; `references/nip55-android-signer.md` |

## Calling it from feature code

Prefer an `Account` method (`commons/.../commons/model/Account.kt`) — e.g. `reactTo(...)`,
`follow(user)` — which builds the template, signs with `account.signer`, updates local
state and broadcasts (`sendMyPublicAndPrivateOutbox`, `sendAutomatic`). If none fits, build
the template from the event class's `build(...)` and `account.signer.sign(template)`.

From a ViewModel, run signer work through `BaseAccountViewModel.launchSigner { … }`
(`commons/.../commons/viewmodels/BaseAccountViewModel.kt`): it runs on IO and turns
`SignerExceptions` into user notices, so don't add your own catch-and-toast. Never retry a
sign yourself: a timeout usually means the user didn't answer in time.

## Login / choosing a signer

- **nsec / hex / ncryptsec** → `NostrSignerInternal`.
- **`bunker://…`** → `NostrSignerRemote.fromBunkerUri(bunkerUri, signer, client)` (`signer`
  is a fresh `NostrSignerInternal` transport key), then `suspend fun connect()`.
- **NIP-55 app** → `ExternalSignerLogin.createIntent(...)`, launch it, then
  `ExternalSignerLogin.parseResult(data)` for the pubkey and package; build
  `NostrSignerExternal(pubKey, packageName, contentResolver)`.

The login form is shared: `commonsUI/.../commons/account/ui/login/` (`LoginScreen`,
`LoginViewModel`, `RemoteSignerLogin`, `KeyTextField`, …) driving
`commons/.../commons/account/AccountSessionManager.kt`. The Android signer-app button,
`amethyst/.../ui/screen/loggedOff/login/ExternalSignerButton.kt`, reaches the form through
`AppPlatform.ExternalSignerLoginButton` (`commonsUI/.../commons/ui/platform/AppPlatform.kt`,
implemented in `amethyst/.../ui/platform/AndroidAppPlatform.kt`).

## Trade-offs

| Signer | Latency | Offline | Key location | UX |
|---|---|---|---|---|
| Internal | µs | yes | app memory | no prompts |
| Remote (NIP-46) | 100 ms – seconds | no (bunker relay must be reachable) | bunker | occasional approvals |
| External (NIP-55) | 100–500 ms | yes | other app | prompt per sign unless pre-approved |

## Gotchas

- **Timeouts are real and long**: `RemoteSignerManager` waits 65 s per request (one retry);
  the NIP-55 foreground path waits 30 s (`IntentRequestManager.foregroundApprovalTimeout`).
  Anything that stamps a time before asking to sign (NIP-98, NIP-42) can expire during the
  prompt — sign right before use.
- **Bunker identity ≠ transport key.** `NostrSignerRemote.pubKey` is the bunker's
  `get_public_key` answer (or `bindUserPubkey(...)` from a saved account); until bound it is the
  transport key. Self-encryption keyed off the wrong one breaks private lists and drafts.
- **External signer needs a foreground Activity** (`IActivityLauncher`); a background caller
  without pre-approved permissions gets `RunningOnBackgroundWithoutAutomaticPermissionException`.
- **NIP-04 is legacy** — new DM code is NIP-17 → `nip44Encrypt`.
- `signPsbt` is unsupported on remote bunkers and older NIP-55 apps; catch
  `UnsupportedMethodException`.

## References

- `references/nip46-remote-signer.md` — bunker request/response taxonomy, connection flow.
- `references/nip55-android-signer.md` — foreground/background transports, command types.
- Related skills: quartz's `nostr-expert` (crypto under the signers), `account-state` (`Account`),
  `android-expert` (activity/intent plumbing).


---
Source attribution: vitorpamplona
Original project: https://github.com/vitorpamplona/amethyst/blob/3cbe201baa37fb15cd81cfff6800ab97c7b4a1f9/.claude/skills/auth-signers/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Copyright (c) 2023 Vitor Pamplona

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Mega AI Hub resource metadata

Creator / publisher: vitorpamplona
Original project: https://github.com/vitorpamplona/amethyst/blob/3cbe201baa37fb15cd81cfff6800ab97c7b4a1f9/.claude/skills/auth-signers/SKILL.md
Attribution basis: Source repository record

Fields of work: Development & Engineering, Product Management
Roles: Backend Developer, Mobile Developer, Product Manager
Specialties: Backend, Mobile
Tools: Amethyst
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: 71b9e0deeebb4adf7fde3399ec129abf91f12f4b9c3831cb66200988cdec048a