In my app on back-end the next code is used to get signer:

const { InMemorySigner } = require('@taquito/signer');

const signer = InMemorySigner.fromSecretKey(
  signingKey,
  TEZOS_SERVICE_PASSPHRASE
)

where TEZOS_SERVICE_PASSPHRASE - some passphrase, that need to be used on front-end to encrypt secret key. According to Taquito documentation https://tezostaquito.io/typedoc/classes/_taquito_signer.inmemorysigner.html, second param is a Passphrase to decrypt the private key if it is encrypted. But how can I encrypt secret key using passphrase on front-end?