Unable to resolve module crypto

Add rn-nodeify to your devDependencies in package.json:

"devDependencies": {
  "rn-nodeify": "^6.0.1"
}

Add the following to the scripts section of the same file:

"scripts": {
  …
  "postinstall": "node_modules/.bin/rn-nodeify --install crypto --hack"
}

npm i --save react-native-crypto
# install peer deps 
npm i --save react-native-randombytes
react-native link react-native-randombytes
# install latest rn-nodeify 
npm i --save-dev mvayngrib/rn-nodeify
# install node core shims and recursively hack package.json files 
# in ./node_modules to add/update the "browser"/"react-native" field with relevant mappings 
./node_modules/.bin/rn-nodeify --hack --install