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API Reference

Crypto

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

Platform Compatibility

Android DeviceAndroid EmulatoriOS DeviceiOS SimulatorWeb

Installation

expo install expo-crypto

If you're installing this in a bare React Native app, you should also follow these additional 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 function runCrypto() {
      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<string>
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
NameTypeDescription
algorithmCryptoDigestAlgorithmTransforms a value into a fixed-size hash (usually shorter than the initial value).
datastringThe value that will be used to generate a digest.
optionsCryptoDigestOptionsFormat of the digest string. Defaults to: CryptoDigestOptions.HEX
Returns
NameTypeDescription
digestPromise<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.
NameTypeDescriptionCollision Resistant🍎 iOS💚 Android💻 Web
SHA1string160 bits❌✅✅✅
SHA256string256 bits✅✅✅✅
SHA384string384 bits✅✅✅✅
SHA512string512 bits✅✅✅✅
MD2string128 bits❌✅❌❌
MD4string128 bits❌✅❌❌
MD5string128 bits❌✅✅❌

CryptoEncoding

NameType🍎 iOS💚 Android💻 Web
HEX'hex'✅✅✅
BASE64'base64'✅✅✅
Base64 Format
  • Has trailing padding.
  • Does not wrap lines.
  • Does not have a trailing newline.

CryptoDigestOptions

NameTypeDescription🍎 iOS💚 Android💻 Web
encodingCryptoEncodingFormat the digest is returned in✅✅✅

Error Codes

CodeDescription
ERR_CRYPTO_UNAVAILABLE(Web only) Access to the WebCrypto API is restricted to secure origins (https).
ERR_CRYPTO_DIGESTAn invalid encoding type provided.