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Crypto

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

Platform Compatibility

Android Device	Android Emulator	iOS Device	iOS Simulator	Web
✅	✅	✅	✅	✅

Installation

expo install expo-crypto

To use this in a bare React Native app, follow the installation instructions.

Usage

import React, { useEffect } from 'react';
import { 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... */
    })();
    runCrypto();
  }, []);

  return (
    <View
      style={{
        flex: 1,
        backgroundColor: '#fff',
        alignItems: 'center',
        justifyContent: 'center',
      }}>
      <Text>Crypto Module Example</Text>
    </View>
  );
}

API

import * as Crypto from 'expo-crypto';

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

digestStringAsync(
  algorithm: CryptoDigestAlgorithm,
  data: string,
  options: CryptoDigestOptions = { encoding: CryptoEncoding.HEX }
): Promise

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.

🍎 iOS	💚 Android	💻 Web
✅	✅	✅

Parameters

Name	Type	Description
algorithm	`CryptoDigestAlgorithm`	Transforms a value into a fixed-size hash (usually shorter than the initial value).
data	`string`	The value that will be used to generate a digest.
options	`CryptoDigestOptions`	Format of the digest string. Defaults to: `CryptoDigestOptions.HEX`

Returns

Name	Type	Description
digest	`Promise<string>`	Resolves into a value representing the hashed input.

Error Codes

ERR_CRYPTO_UNAVAILABLE - (Web only) Access to the WebCrypto API is restricted to secure origins (https). You can run your web project from a secure origin with expo start --https.
ERR_CRYPTO_DIGEST - An invalid encoding type provided.

Example

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

Types

`CryptoDigestAlgorithm`

Cryptographic hash function is an algorithm that can be used to generate a checksum value. They have a variety of applications in cryptography.

Cryptographic hash functions like SHA1, MD5 are vulnerable! Attacks have been proven to significantly reduce their collision resistance.

Name	Type	Description	Collision Resistant	🍎 iOS	💚 Android	💻 Web
SHA1	string	`160` bits	❌	✅	✅	✅
SHA256	string	`256` bits	✅	✅	✅	✅
SHA384	string	`384` bits	✅	✅	✅	✅
SHA512	string	`512` bits	✅	✅	✅	✅
MD2	string	`128` bits	❌	✅	✅	❌
MD4	string	`128` bits	❌	✅	✅	❌
MD5	string	`128` bits	❌	✅	✅	❌

`CryptoEncoding`

Name	Type	🍎 iOS	💚 Android	💻 Web
HEX	`'hex'`	✅	✅	✅
BASE64	`'base64'`	✅	✅	✅

Base64 Format

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

`CryptoDigestOptions`

Name	Type	Description	🍎 iOS	💚 Android	💻 Web
encoding	`CryptoEncoding`	Format the digest is returned in	✅	✅	✅

Error Codes

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