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mobilecritical PriorityID: capacitor-7-hardware-keystore-attestation-bridge

Capacitor 7 Hardware-Backed Keystore Attestation and Zero-Leakage IPC Bridge

Enforces strict isolation of cryptographic material by delegating key generation, storage, and signing exclusively to hardware-backed enclaves (Android StrongBox/TEE and iOS Secure Enclave). Prohibits transmission of raw private keys, seeds, or unencrypted secrets across the JavaScript-to-Native IPC bridge, restricting bridge payloads to opaque key aliases, public keys, and cryptographic attestation statements.

Prohibited Anti-Pattern: Exposing Raw Cryptographic Seeds or Performing Software Key Generation across the Capacitor WebView IPC Bridge

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---
description: Capacitor 7 Hardware-Backed Keystore Attestation and Zero-Leakage IPC Bridge - Enforces strict isolation of cryptographic material by delegating key generation, storage, and signing exclusively to hardware-backed enclaves (Android StrongBox/TEE and iOS Secure Enclave). Prohibits transmission of raw private keys, seeds, or unencrypted secrets across the JavaScript-to-Native IPC bridge, restricting bridge payloads to opaque key aliases, public keys, and cryptographic attestation statements.
globs: src/plugins/**/*.{ts,tsx,java,kt,swift}, src/services/**/*.{ts,tsx}, android/app/src/main/java/**/*.kt, ios/App/App/**/*.swift
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/capacitor-7-hardware-keystore-attestation-bridge"
---

# Capacitor 7 Hardware-Backed Keystore Attestation and Zero-Leakage IPC Bridge

> **Severity**: CRITICAL | **Category**: mobile
> **Anti-Pattern Warning**: Exposing Raw Cryptographic Seeds or Performing Software Key Generation across the Capacitor WebView IPC Bridge

## System Constraints
You are a Principal Mobile Architect enforcing Capacitor 7 Secure Hardware Keystore and Bridge Architecture. Enforce absolute key isolation within hardware-backed security modules (Apple Secure Enclave and Android TEE/StrongBox). Under no circumstances allow raw cryptographic seeds, private key buffers, or entropy pools to be generated in or serialized across the Capacitor JavaScript-to-native IPC bridge. Mandate hardware-attested public key exchanges and opaque key alias signing protocols.

## Strict Guidelines
- Engineers MUST ALWAYS generate asymmetric key pairs inside hardware-isolated modules (Android KeyStore with KeyGenParameterSpec StrongBox/TEE, or iOS Secure Enclave via kSecAttrTokenIDSecureEnclave).
- Engineers MUST NOT expose methods in Capacitor bridge plugins that return, import, or accept raw private keys, seed phrases, or unencrypted symmetric keys across the IPC boundary.
- Code MUST pass only non-sensitive key aliases, public keys (DER/PEM format), and hardware attestation chains (X.509 cert chains or App Attest tokens) over the Capacitor bridge to the WebView context.
- Services MUST execute signing and decryption operations entirely within native code, returning only the resulting signature or decrypted payload reference to JavaScript.
- Bridge interfaces MUST validate and sanitize all payload inputs before passing them to native cryptographic providers, preventing injection and buffer overrun vulnerabilities.
- Components NEVER store sensitive cryptographic material in WebView localStorage, IndexedDB, or standard unencrypted SharedPreferences / NSUserDefaults.

## Bad vs Good Implementations
### Hardware Enclave Bridge Contract vs. Insecure Software Seed IPC

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Raw mnemonic seeds and private keys transit the Capacitor IPC bridge and reside in unpinned JavaScript memory, exposing them to WebView XSS exploits, memory scrapers, and insecure device logs.
```typescript
import { registerPlugin } from '@capacitor/core';

// VULNERABLE: Bridge contract accepts raw seeds and exports private keys into WebView memory
export interface InsecureCryptoPlugin {
  generateWallet(options: { mnemonic: string }): Promise<{
    privateKeyHex: string;
    publicKeyHex: string;
    address: string;
  }>;
  signTransaction(options: {
    privateKeyHex: string;
    payload: string;
  }): Promise<{ signature: string }>;
}

export const CryptoBridge = registerPlugin<InsecureCryptoPlugin>('InsecureCrypto');
```

#### Production Standard (Correct)
> **Standard**: The cryptographic key pair is created and permanently bounded inside the native Secure Enclave or StrongBox Keystore. The bridge only receives the opaque key alias, public key, and verifiable hardware attestation chain.
```typescript
import { registerPlugin } from '@capacitor/core';

export interface AttestedKeyResult {
  alias: string;
  publicKeySpkiBase64: string;
  attestationChain: string[]; // Base64 DER-encoded X.509 certs from TEE/StrongBox or DeviceCheck/AppAttest
  hardwareSecurityLevel: 'STRONGBOX' | 'TEE' | 'SECURE_ENCLAVE';
}

export interface SecureSignRequest {
  alias: string;
  dataBase64: string;
  userAuthenticationRequired?: boolean;
}

export interface SecureSignResult {
  signatureBase64: string;
}

// HARDENED: Private key never leaves the hardware enclave; only handles and signatures cross the bridge
export interface SecureKeystorePlugin {
  generateHardwareKey(options: {
    alias: string;
    requireBiometrics: boolean;
    attestationChallenge: string;
  }): Promise<AttestedKeyResult>;
  signWithHardwareKey(options: SecureSignRequest): Promise<SecureSignResult>;
  deleteHardwareKey(options: { alias: string }): Promise<{ success: boolean }>;
}

export const SecureKeystore = registerPlugin<SecureKeystorePlugin>('SecureKeystore');
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

Mobile Security Analysis Server
Analyzes native and cross-platform mobile bindings for IPC data leakage and cryptographic misuse.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

Capacitor Plugin Security Linter
Validates Capacitor bridge method signatures against zero-leakage security boundaries.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Capacitor 7 Hardware-Backed Keystore Attestation and Zero-Leakage IPC Bridge

Capacitor 7 Hardware-Backed Keystore Attestation and Zero-Leakage IPC Bridge defines an industrial-grade behavioral standard for mobile engineering. Enforces strict isolation of cryptographic material by delegating key generation, storage, and signing exclusively to hardware-backed enclaves (Android StrongBox/TEE and iOS Secure Enclave). Prohibits transmission of raw private keys, seeds, or unencrypted secrets across the JavaScript-to-Native IPC bridge, restricting bridge payloads to opaque key aliases, public keys, and cryptographic attestation statements. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Exposing Raw Cryptographic Seeds or Performing Software Key Generation across the Capacitor WebView IPC Bridge Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftExposing Raw Cryptographic Seeds or Performing Software Key Generation across the Capacitor WebView IPC BridgeCritical
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

Engineers MUST ALWAYS generate asymmetric key pairs inside hardware-isolated modules (Android KeyStore with KeyGenParameterSpec StrongBox/TEE, or iOS Secure Enclave via kSecAttrTokenIDSecureEnclave).

Engineers MUST ALWAYS generate asymmetric key pairs inside hardware-isolated modules (Android KeyStore with KeyGenParameterSpec StrongBox/TEE, or iOS Secure Enclave via kSecAttrTokenIDSecureEnclave).

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Engineers MUST NOT expose methods in Capacitor bridge plugins that return, import, or accept raw private keys, seed phrases, or unencrypted symmetric keys across the IPC boundary.

Engineers MUST NOT expose methods in Capacitor bridge plugins that return, import, or accept raw private keys, seed phrases, or unencrypted symmetric keys across the IPC boundary.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Code MUST pass only non-sensitive key aliases, public keys (DER/PEM format), and hardware attestation chains (X.509 cert chains or App Attest tokens) over the Capacitor bridge to the WebView context.

Code MUST pass only non-sensitive key aliases, public keys (DER/PEM format), and hardware attestation chains (X.509 cert chains or App Attest tokens) over the Capacitor bridge to the WebView context.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

Services MUST execute signing and decryption operations entirely within native code, returning only the resulting signature or decrypted payload reference to JavaScript.

Services MUST execute signing and decryption operations entirely within native code, returning only the resulting signature or decrypted payload reference to JavaScript.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
5

Bridge interfaces MUST validate and sanitize all payload inputs before passing them to native cryptographic providers, preventing injection and buffer overrun vulnerabilities.

Bridge interfaces MUST validate and sanitize all payload inputs before passing them to native cryptographic providers, preventing injection and buffer overrun vulnerabilities.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
6

Components NEVER store sensitive cryptographic material in WebView localStorage, IndexedDB, or standard unencrypted SharedPreferences / NSUserDefaults.

Components NEVER store sensitive cryptographic material in WebView localStorage, IndexedDB, or standard unencrypted SharedPreferences / NSUserDefaults.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is Capacitor 7 Hardware-Backed Keystore Attestation and Zero-Leakage IPC Bridge critical for AI coding assistants?

Enforces strict isolation of cryptographic material by delegating key generation, storage, and signing exclusively to hardware-backed enclaves (Android StrongBox/TEE and iOS Secure Enclave). Prohibits transmission of raw private keys, seeds, or unencrypted secrets across the JavaScript-to-Native IPC bridge, restricting bridge payloads to opaque key aliases, public keys, and cryptographic attestation statements. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Exposing Raw Cryptographic Seeds or Performing Software Key Generation across the Capacitor WebView IPC Bridge) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

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