Crypto

Crypto is random identifiers, secure random bytes and hashes, bound to expo-crypto. Hermes has no Web Crypto, so crypto.randomUUID() is not there on a device; this is where a UUID or a SHA-256 comes from instead.

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

@Component({
  selector: 'app-new-note',
  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 - throws a MissingModuleError when the service first reaches for it. 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.

Reference

Cryptoservice@ng-native/expo

import { Crypto } from '@ng-native/expo';

Methods

randomUUID(): string

A version 4 UUID, from the platform's secure random source.

digestString(...args: Args<'digestStringAsync'>): Promise<string>

The hash of a string, as hex or base64.

digest(...args: Args<'digest'>): Promise<ArrayBuffer>

The hash of bytes, as Web Crypto's digest answers it.

randomBytes(count: number): Uint8Array

Cryptographically secure random bytes, between 0 and 1024 of them.

randomBytesAsync(count: number): Promise<Uint8Array>

The same, as a promise.

randomValues(array: T): T

Fills an integer typed array with secure random values and hands it back, as Web Crypto's.