Criação de novas APIs | Node.js: API Rest com Express e MongoDB

Olá,

Estou tentando fazer uma api que realiza a criptografia de uma string. Porém, quando tento utilizar var crypto = require('crypto'), dá o erro abaixo.

Mais abaixo, inclui o meu código.

Obrigada.

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    <title>Error</title>
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    <pre>ReferenceError: require is not defined<br> &nbsp; &nbsp;at criptografarSenha (file:///C:/git/CriptografiaOrbitall/src/app.js:34:18)<br> &nbsp; &nbsp;at file:///C:/git/CriptografiaOrbitall/src/app.js:22:5<br> &nbsp; &nbsp;at Layer.handle [as handle_request] (C:\git\CriptografiaOrbitall\node_modules\express\lib\router\layer.js:95:5)<br> &nbsp; &nbsp;at next (C:\git\CriptografiaOrbitall\node_modules\express\lib\router\route.js:137:13)<br> &nbsp; &nbsp;at Route.dispatch (C:\git\CriptografiaOrbitall\node_modules\express\lib\router\route.js:112:3)<br> &nbsp; &nbsp;at Layer.handle [as handle_request] (C:\git\CriptografiaOrbitall\node_modules\express\lib\router\layer.js:95:5)<br> &nbsp; &nbsp;at C:\git\CriptografiaOrbitall\node_modules\express\lib\router\index.js:281:22<br> &nbsp; &nbsp;at param (C:\git\CriptografiaOrbitall\node_modules\express\lib\router\index.js:360:14)<br> &nbsp; &nbsp;at param (C:\git\CriptografiaOrbitall\node_modules\express\lib\router\index.js:371:14)<br> &nbsp; &nbsp;at Function.process_params (C:\git\CriptografiaOrbitall\node_modules\express\lib\router\index.js:416:3)</pre>
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import express from "express";

const app = express();

app.use(express.json());


app.get('/criptografar/:senha', (req, res) => {
    criptografarSenha(req.params.senha)    
})

function criptografarSenha(senha) {
    var crypto = require('crypto')

    // Chave pública
    const publicKey = `AQUI FICARÁ MINHA CHAVE PUBLICA`

    const plaintext = senha

    const encrypt = (publicKey, plaintext) => {
        const buffer = Buffer.from(plaintext, 'utf8')
        const encrypted = crypto.publicEncrypt(publicKey, buffer)
        return encrypted.toString('base64')
    }

    const hash = encrypt(publicKey, plaintext)

    console.log(res.json(hash));
}

export default app;