Crypto

It is the one Expo service that is not inert without its module. An empty identifier is a key every record shares, and an empty hash matches every input, and neither looks wrong until the data is. So without expo-crypto installed, every call throws, and the error names the package.

Install

npx expo install expo-crypto

import { Crypto, CryptoDigestAlgorithm, CryptoEncoding } from '@ng-native/expo/crypto';

The smallest useful example

import { Component, inject, signal } from '@angular/core';
import { Pressable, Text } from '@ng-native/components';
import { Crypto, CryptoDigestAlgorithm } from '@ng-native/expo/crypto';

@Component({
  selector: 'app-new-note',
  imports: [Pressable, Text],
  template: `<pressable (press)="create()"
    ><text>New note {{ id() }}</text></pressable
  >`,
})
export class NewNote {
  private readonly crypto = inject(Crypto);
  protected readonly id = signal('');

  protected async create(): Promise<void> {
    this.id.set(this.crypto.randomUUID());
    console.log(await this.crypto.digestString(CryptoDigestAlgorithm.SHA256, this.id()));
  }
}

What it does

• randomUUID() - a version 4 UUID from the platform's secure random source.
• digestString(algorithm, text, options?) - the hash of a string, as hex by default or base64 with { encoding: CryptoEncoding.BASE64 }.
• digest(algorithm, bytes) - the hash of bytes as an ArrayBuffer, as Web Crypto's digest answers it.
• randomBytes(count) and randomBytesAsync(count) - between 0 and 1024 secure random bytes, as a Uint8Array.
• randomValues(array) - fills an integer typed array with secure random values in place and hands it back, as Web Crypto's getRandomValues does.

CryptoDigestAlgorithm (SHA1, SHA256, SHA384, SHA512, MD5, and on iOS MD2 and MD4) and CryptoEncoding are exported beside the service: the module's own enums, typed as those enums, without loading the module, so code that hashes can run in a test.

AES encryption is not part of the service. aesEncryptAsync and aesDecryptAsync take a key and sealed data that only the module's own AESEncryptionKey and AESSealedData classes make, so code that encrypts imports expo-crypto directly.

Without the module

On iOS and Android, a missing expo-crypto - never installed, or installed without the app being rebuilt since - leaves the service made, so injecting it does not throw. A call, or a read of a value only the module knows, throws a MissingModuleError. Its message names the module and the commands that fix it; see Using a module.

On the web, and in a test that provides no fake, every method throws, or rejects for the promise-returning ones, with an error naming expo-crypto.

In a test

Node has no native modules, so in a test Crypto throws when it is first used, saying so. Provide Crypto.SOURCE with the methods the code under test calls:

const ids = injectService(Ids, {
  providers: [{ provide: Crypto.SOURCE, useValue: { randomUUID: () => 'test-id' } }],
});

Reference