aes-crypto-module.js
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aes-crypto-module.js
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	// @flow

	import { requireNativeModule } from 'expo-modules-core';
	import invariant from 'invariant';

	const KEY_SIZE = 32; // bytes
	const IV_LENGTH = 12; // bytes, IV - unique Initialization Vector (nonce)
	const TAG_LENGTH = 16; // bytes - GCM auth tag

	const AESCryptoModule: {
	+generateKey: (destination: Uint8Array) => void,
	+encrypt: (
	key: Uint8Array,
	data: Uint8Array,
	destination: Uint8Array,
	) => void,
	+decrypt: (
	key: Uint8Array,
	data: Uint8Array,
	destination: Uint8Array,
	) => void,
	} = requireNativeModule('AESCrypto');

	export function generateKey(): Uint8Array {
	const keyBuffer = new Uint8Array(KEY_SIZE);
	AESCryptoModule.generateKey(keyBuffer);
	return keyBuffer;
	}

	export function encrypt(key: Uint8Array, data: Uint8Array): Uint8Array {
	const sealedDataBuffer = new Uint8Array(data.length + IV_LENGTH + TAG_LENGTH);
	AESCryptoModule.encrypt(key, data, sealedDataBuffer);
	return sealedDataBuffer;
	}

	export function decrypt(key: Uint8Array, data: Uint8Array): Uint8Array {
	invariant(data.length >= IV_LENGTH + TAG_LENGTH, 'Invalid data length');
	const plaintextBuffer = new Uint8Array(data.length - IV_LENGTH - TAG_LENGTH);
	AESCryptoModule.decrypt(key, data, plaintextBuffer);
	return plaintextBuffer;
	}