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alknet/docs/architecture/secret-service.md
glm-5.1 d3633b7839 docs: complete Phase 0 architecture — spec updates, review fixes, and link portability
Update four existing specs (overview, server, napi-and-pubsub, call-protocol) to
reflect Phase 0 decisions: three-layer model, IdentityProvider, ForwardingPolicy,
OperationEnv, static/dynamic config split. Review all 9 Phase 0a ADRs (026-034)
for consistency. Fix 4 critical issues from architecture review: missing OQ-SVC-05
in open-questions.md, deprecated hub terminology, undefined AuthService and noq
terms. Replace inline OQ text with cross-references per format rules. Add
ConfigServiceImpl definition to configuration.md. Port absolute workspace paths
to project-relative links by copying referenced docs (feasibility, certbot,
fail2ban, event_source_types) into docs/research/.
2026-06-07 11:27:52 +00:00

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---
status: draft
last_updated: 2026-06-07
---
# Secret Service
## What
The `alknet-secret` crate provides BIP39 mnemonic generation, SLIP-0010 Ed25519
HD key derivation, AES-256-GCM encryption for external credentials, and the
`SecretProtocol` irpc service. It is the only component that holds the master
seed phrase.
## Why
Operations like SSH key generation, API key storage, and Ethereum transaction
signing all need deterministic key derivation from a single root of trust. The
seed phrase is the single recovery mechanism — from it, all self-generated
secrets can be derived on demand. External credentials (third-party API keys,
OAuth tokens) cannot be derived and must be stored encrypted, with the
encryption key itself derived from the seed.
The secret service isolates this responsibility: no other crate sees the seed,
and derived keys are provided on demand through an irpc service interface.
## Architecture
### Security Model
| State | What's in memory | What's on disk |
|-------|-----------------|---------------|
| Locked | Nothing | Encrypted database, derivation path metadata |
| Unlocked | Master seed in RAM | Same (seed is never persisted) |
| After use | Derived keys cached in RAM | Derivation paths only |
The seed phrase is entered once (at node startup or via `Unlock` call), held
only in RAM, and never written to disk. The `Lock` call purges the seed and all
cached derived keys from memory.
### SecretProtocol irpc Service
```rust
#[rpc_requests(message = SecretMessage)]
#[derive(Debug, Serialize, Deserialize)]
enum SecretProtocol {
#[rpc(tx=oneshot::Sender<DerivedKey>)]
#[wrap(DeriveEd25519)]
DeriveEd25519 { path: String },
#[rpc(tx=oneshot::Sender<DerivedKey>)]
#[wrap(DeriveEncryptionKey)]
DeriveEncryptionKey { path: String },
#[rpc(tx=oneshot::Sender<DerivedKey>)]
#[wrap(DeriveEthereumKey)]
DeriveEthereumKey { path: String },
#[rpc(tx=oneshot::Sender<Vec<u8>>)]
#[wrap(DerivePassword)]
DerivePassword { path: String, length: usize },
#[rpc(tx=oneshot::Sender<EncryptedData>)]
#[wrap(Encrypt)]
Encrypt { plaintext: String, key_version: u32 },
#[rpc(tx=oneshot::Sender<String>)]
#[wrap(Decrypt)]
Decrypt { encrypted: EncryptedData },
#[rpc(tx=oneshot::Sender<()>)]
#[wrap(Lock)]
Lock,
#[rpc(tx=oneshot::Sender<()>)]
#[wrap(Unlock)]
Unlock { passphrase: String },
}
#[derive(Debug, Serialize, Deserialize)]
struct DerivedKey {
key_type: KeyType,
private_key: Vec<u8>,
public_key: Vec<u8>,
}
#[derive(Debug, Serialize, Deserialize)]
enum KeyType {
Ed25519,
Aes256Gcm,
Secp256k1,
}
#[derive(Debug, Serialize, Deserialize)]
struct EncryptedData {
key_version: u32,
salt: String, // Base64-encoded
iv: String, // Base64-encoded
data: String, // Base64-encoded
}
```
### BIP39 Mnemonic and Seed Derivation
```rust
let mnemonic = Mnemonic::from_phrase(&phrase, Language::English)?;
let seed = mnemonic.to_seed(Some(&passphrase));
let master_key = ExtendedPrivKey::new_master(Network::Alknet, &seed)?;
```
### SLIP-0010 Ed25519 HD Key Derivation
The `74'` coin type is unallocated per SLIP-0044 and reserved for alknet.
### Derivation Path Constants
| Path | Purpose | Curve/Algorithm |
|------|---------|----------------|
| `m/74'/0'/0'/0'` | Primary identity keypair | Ed25519 (alknet auth) |
| `m/74'/0'/0'/{n}'` | Worker/device identity | Ed25519 |
| `m/74'/0'/1'/0'` | SSH host key | Ed25519 |
| `m/74'/1'/0'/{hash}'` | Site-specific password | Deterministic |
| `m/74'/2'/0'/0'` | Encryption key for external credentials | AES-256-GCM |
| `m/44'/60'/0'/0/0` | Ethereum signing key | secp256k1 |
### AES-256-GCM Encryption for External Credentials
External credentials (API keys, OAuth tokens) that cannot be derived are
encrypted using a key derived from the seed at path `m/74'/2'/0'/0'`. The
`EncryptedData` type stores the key version, salt, IV, and ciphertext. This
format is compatible with the existing `@alkdev/storage` `EncryptedDataSchema`.
1. The secret service derives an AES-256-GCM key via path `m/74'/2'/0'/0'`
2. External credentials are encrypted with this key
3. The encrypted data is stored as a `SecretNode` in the metagraph
4. Only the derivation path and key version are stored in plain attributes
5. The seed phrase (or derived encryption key) is held only by the secret
service — never in the database
### Deployment Topologies
**Minimal (single node, CLI)**: Secret service runs in the same process. Seed
phrase entered at startup. All keys derived locally. No irpc overhead.
**Production (head node)**: Secret service runs on a dedicated node or as a
local irpc service. Workers request derived keys via irpc over QUIC. The seed
never leaves the secret service node.
## Constraints
- The seed phrase is never persisted to disk. It is entered at startup or via
`Unlock` and held only in RAM.
- `Lock` purges the seed and all cached derived keys from memory.
- alknet-secret does not depend on alknet-core or alknet-storage. It is fully
independent.
- The `EncryptedData` wire format (key_version, salt, iv, data) is shared with
alknet-storage for compatibility, but this is type-level compatibility — not a
crate dependency.
- Per ADR-032, the secret service's Honker streams (key derivation notifications)
stay within the service boundary. External consumers use irpc calls or call
protocol operations that project to integration events.
- The irpc service defines the wire format for in-cluster communication
(postcard serialization). For call protocol exposure (e.g.,
`/head/secrets/derive`), the service is wrapped in an operation that serializes
to JSON.
## Open Questions
- **OQ-SVC-01**: Should the secret service support multiple seed phrases (one
per tenant)? See [open-questions.md](open-questions.md).
- **OQ-SVC-02**: Should service protocols use postcard (binary) or JSON for
remote calls? See [open-questions.md](open-questions.md).
- **OQ-SVC-03**: How does the secret service integrate with the existing
`EncryptedDataSchema` from `@alkdev/storage`? See [open-questions.md](open-questions.md).
- **OQ-SVC-04**: Should workers cache derived keys locally? See [open-questions.md](open-questions.md).
## Design Decisions
| ADR | Decision | Summary |
|-----|----------|---------|
| [027](decisions/027-crate-decomposition.md) | Crate decomposition | alknet-secret is independent of core and storage |
| [032](decisions/032-event-boundary-discipline.md) | Event boundary | Secret service domain events stay internal |
## References
- [research/services.md](../research/services.md) — SecretProtocol definition, DerivedKey, KeyType
- [research/storage.md](../research/storage.md) — Secrets section, derivation paths, EncryptedData
- [research/integration-plan.md](../research/integration-plan.md) — Phase 2.1
- SLIP-0010 — https://github.com/satoshilabs/slips/blob/master/slip-0010.md
- BIP39 — https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki