useDeriveEntropy

useDeriveEntropy derives deterministic entropy from the user's wallet (RFC-0007). Call derive(key) with a Uint8Array; it resolves to 32 bytes that are stable across sessions and devices: the same key with the same wallet always yields the same bytes, while a different key or a different wallet yields unrelated ones. The hook also returns mutation state (isPending, error, data, reset).

That property makes it the building block for secrets you never have to store or sync: derive an encryption key for user data, a seed for an app-specific identity, or a deterministic salt, and re-derive it on any device where the wallet is available. Use distinct, namespaced keys (my-app/settings-encryption/v1) so unrelated features get unrelated entropy.

This is a host feature: standalone, derive rejects with HostUnavailableError, so gate it on useIsHost.

Usage

import { useDeriveEntropy } from "@use-truapi/react";

function UnlockNotes({ onKey }: { onKey: (key: Uint8Array) => void }) {
  const { derive, isPending, error } = useDeriveEntropy();

  async function onUnlock() {
    const entropy = await derive(
      new TextEncoder().encode("my-app/notes-encryption/v1"),
    );
    onKey(entropy); // 32 bytes, feed into your cipher of choice
  }

  return (
    <>
      <button type="button" onClick={onUnlock} disabled={isPending}>
        {isPending ? "Deriving key…" : "Unlock notes"}
      </button>
      {error && <p role="alert">{error.message}</p>}
    </>
  );
}

<script setup lang="ts">
import { useDeriveEntropy } from "@use-truapi/vue";

const emit = defineEmits<{ key: [entropy: Uint8Array] }>();
const { derive, isPending, error } = useDeriveEntropy();

async function onUnlock() {
  const entropy = await derive(
    new TextEncoder().encode("my-app/notes-encryption/v1"),
  );
  emit("key", entropy); // 32 bytes, feed into your cipher of choice
}
</script>

<template>
  <button type="button" :disabled="isPending" @click="onUnlock">
    {{ isPending ? "Deriving key…" : "Unlock notes" }}
  </button>
  <p v-if="error" role="alert">{{ error.message }}</p>
</template>

See also

• useIsHost gates the affordance when the app also runs standalone.
• useHostStorage is a natural place to keep data encrypted with a derived key.

API reference

React

function useDeriveEntropy(options?): NamedMutation<Uint8Array<ArrayBufferLike>, Uint8Array<ArrayBufferLike>> & object;

RFC-0007 deterministic entropy — same key, same wallet ⇒ same 32 bytes: derive(key).

Parameters

Returns

NamedMutation<Uint8Array<ArrayBufferLike>, Uint8Array<ArrayBufferLike>> & object

Vue

function useDeriveEntropy(options?): NamedMutation<Uint8Array<ArrayBufferLike>, Uint8Array<ArrayBufferLike>> & object;

RFC-0007 deterministic entropy — same key, same wallet ⇒ same 32 bytes: derive(key).

Parameters

Returns

NamedMutation<Uint8Array<ArrayBufferLike>, Uint8Array<ArrayBufferLike>> & object