Expo Crypto

GitHub

npm

A universal library for crypto operations.

Android

iOS

tvOS

Web

Bundled version:

~14.1.1

expo-crypto enables you to hash data in an equivalent manner to the Node.js core crypto API.

Installation

Terminal

- npx expo install expo-crypto

If you are installing this in an existing React Native app, make sure to install expo in your project.

Usage

Basic Crypto usage

import { useEffect } from 'react';
import { StyleSheet, View, Text } from 'react-native';
import * as Crypto from 'expo-crypto';

export default function App() {
  useEffect(() => {
    (async () => {
      const digest = await Crypto.digestStringAsync(
        Crypto.CryptoDigestAlgorithm.SHA256,
        'GitHub stars are neat 🌟'
      );
      console.log('Digest: ', digest);
      /* Some crypto operation... */
    })();
  }, []);

  return (
    <View style={styles.container}>
      <Text>Crypto Module Example</Text>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
});

API

import * as Crypto from 'expo-crypto';

Methods

`Crypto.digest(algorithm, data)`

Parameter	Type	Description
algorithm	`CryptoDigestAlgorithm`	The cryptographic hash function to use to transform a block of data into a fixed-size output.
data	`BufferSource`	The value that will be used to generate a digest.

The digest() method of Crypto generates a digest of the supplied TypedArray of bytes data with the provided digest algorithm. A digest is a short fixed-length value derived from some variable-length input. Cryptographic digests should exhibit collision-resistance, meaning that it's very difficult to generate multiple inputs that have equal digest values. On web, this method can only be called from a secure origin (HTTPS) otherwise, an error will be thrown.

Returns:

Promise<ArrayBuffer>

A Promise which fulfills with an ArrayBuffer representing the hashed input.

Example

const array = new Uint8Array([1, 2, 3, 4, 5]);
const digest = await Crypto.digest(Crypto.CryptoDigestAlgorithm.SHA512, array);
console.log('Your digest: ' + digest);

`Crypto.digestStringAsync(algorithm, data, options)`

Parameter	Type	Description
algorithm	`CryptoDigestAlgorithm`	The cryptographic hash function to use to transform a block of data into a fixed-size output.
data	`string`	The value that will be used to generate a digest.
options(optional)	`CryptoDigestOptions`	Format of the digest string. Defaults to: `CryptoDigestOptions.HEX`.

The digestStringAsync() method of Crypto generates a digest of the supplied data string with the provided digest algorithm. A digest is a short fixed-length value derived from some variable-length input. Cryptographic digests should exhibit collision-resistance, meaning that it's very difficult to generate multiple inputs that have equal digest values. You can specify the returned string format as one of CryptoEncoding. By default, the resolved value will be formatted as a HEX string. On web, this method can only be called from a secure origin (HTTPS) otherwise, an error will be thrown.

Returns:

Promise<Digest>

Return a Promise which fulfills with a value representing the hashed input.

Example

const digest = await Crypto.digestStringAsync(
  Crypto.CryptoDigestAlgorithm.SHA512,
  '🥓 Easy to Digest! 💙'
);

`Crypto.getRandomBytes(byteCount)`

Parameter	Type	Description
byteCount	`number`	A number within the range from `0` to `1024`. Anything else will throw a `TypeError`.

Generates completely random bytes using native implementations. The byteCount property is a number indicating the number of bytes to generate in the form of a Uint8Array. Falls back to Math.random during development to prevent issues with React Native Debugger.

Returns:

Uint8Array

An array of random bytes with the same length as the byteCount.

`Crypto.getRandomBytesAsync(byteCount)`

Parameter	Type	Description
byteCount	`number`	A number within the range from `0` to `1024`. Anything else will throw a `TypeError`.

Generates completely random bytes using native implementations. The byteCount property is a number indicating the number of bytes to generate in the form of a Uint8Array.

Returns:

Promise<Uint8Array>

A promise that fulfills with an array of random bytes with the same length as the byteCount.

`Crypto.getRandomValues(typedArray)`

Parameter	Type	Description
typedArray	`T`	An integer based `TypedArray` to fill with cryptographically secure random values. It modifies the input array in place.

The getRandomValues() method of Crypto fills a provided TypedArray with cryptographically secure random values.

Returns:

T

The input array filled with cryptographically secure random values.

Example

const byteArray = new Uint8Array(16);
Crypto.getRandomValues(byteArray);
console.log('Your lucky bytes: ' + byteArray);

`Crypto.randomUUID()`

The randomUUID() method returns a unique identifier based on the V4 UUID spec (RFC4122). It uses cryptographically secure random values to generate the UUID.

Returns:

string

A string containing a newly generated UUIDv4 identifier

Example

const UUID = Crypto.randomUUID();
console.log('Your UUID: ' + UUID);

Types

`CryptoDigestOptions`

Property	Type	Description
encoding	`CryptoEncoding`	Format the digest is returned in.

`Digest`

Type: string

Enums

`CryptoDigestAlgorithm`

Cryptographic hash function

`MD2`

Only for:

iOS

CryptoDigestAlgorithm.MD2 ＝ "MD2"

128 bits.

`MD4`

Only for:

iOS

CryptoDigestAlgorithm.MD4 ＝ "MD4"

128 bits.

`MD5`

Only for:

Android

iOS

CryptoDigestAlgorithm.MD5 ＝ "MD5"

128 bits.

`SHA1`

CryptoDigestAlgorithm.SHA1 ＝ "SHA-1"

160 bits.

`SHA256`

CryptoDigestAlgorithm.SHA256 ＝ "SHA-256"

256 bits. Collision Resistant.

`SHA384`

CryptoDigestAlgorithm.SHA384 ＝ "SHA-384"

384 bits. Collision Resistant.

`SHA512`

CryptoDigestAlgorithm.SHA512 ＝ "SHA-512"

512 bits. Collision Resistant.

`CryptoEncoding`

`BASE64`

CryptoEncoding.BASE64 ＝ "base64"

Has trailing padding. Does not wrap lines. Does not have a trailing newline.

`HEX`

CryptoEncoding.HEX ＝ "hex"

Error codes

Code	Description
`ERR_CRYPTO_UNAVAILABLE`	Web Only. Access to the WebCrypto API is restricted to secure origins (localhost/https).
`ERR_CRYPTO_DIGEST`	An invalid encoding type provided.