identity-derive
Derive a child Nostr identity from the master key by purpose and index. Deterministic — same inputs always produce the same npub. Returns { npub, purpose, index }. Use identity_switch after deriving to operate as the new identity.
This record as markdown: /tools/dev-forgesworn-bray/identity-derive.md
What identity-derive does on Nostr Bray
AI agents call identity-derive to retrieve information from Nostr Bray without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why identity-derive is rated Low
The tool performs a deterministic cryptographic derivation — it computes a child key from a master key and returns the resulting public identity (npub). It does not store, modify, or activate any state by itself; it purely computes and returns values. However, it exposes derived key material (npub) from a master key, which has moderate security implications if misused.
From the tool's definition Derive a child Nostr identity from the master key by purpose and index. Deterministic — same inputs always produce the same npub. Returns { npub, purpose, index }.
Attacks that exploit this kind of access
The rule that runs identity-derive safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Nostr Bray, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For identity-derive, this is the rule to start with:
identity-derive is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Nostr Bray, apply this rule, and every identity-derive call is checked against it from then on.
Questions about identity-derive
Derive a child Nostr identity from the master key by purpose and index. Deterministic — same inputs always produce the same npub. Returns { npub, purpose, index }. Use identity_switch after deriving to operate as the new identity. It is categorised as a Read tool in the Nostr Bray MCP Server, which means it retrieves data without modifying state.
Register the Nostr Bray MCP server in PolicyLayer and add a rule for identity-derive: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Nostr Bray. Nothing to install.
identity-derive is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the identity-derive rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for identity-derive. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
identity-derive is provided by the Nostr Bray MCP server (nostr-bray). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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