How to use the sodium-native.crypto_secretbox_open_easy function in sodium-native

export function vaultFromHexString(organizationVaultSecret: string, dataHexString: string): Vault {
  // The nonce/salt is prepended to the actual ciphertext:
  const dataBuffer = Buffer.from(dataHexString, "hex");
  const nonceBuffer = dataBuffer.slice(0, sodium.crypto_secretbox_NONCEBYTES);
  const cipherBuffer = dataBuffer.slice(sodium.crypto_secretbox_NONCEBYTES);

  const keyBuffer = toKeyBuffer(organizationVaultSecret);

  const plaintextBuffer = Buffer.alloc(cipherBuffer.length - sodium.crypto_secretbox_MACBYTES);
  if (!sodium.crypto_secretbox_open_easy(plaintextBuffer, cipherBuffer, nonceBuffer, keyBuffer)) {
    throw Error("Vault decryption failed!");
  }

  const vaultString = plaintextBuffer.toString();
  const vault: Vault = JSON.parse(vaultString);
  return vault;
}

export function decrypt(
  organizationSecret: string,
  hexEncodedCiphertext: string,
): Result.Type {
  // The nonce/salt is prepended to the actual ciphertext:
  const dataBuffer = Buffer.from(hexEncodedCiphertext, "hex");
  const nonceBuffer = dataBuffer.slice(0, sodium.crypto_secretbox_NONCEBYTES);
  const cipherBuffer = dataBuffer.slice(sodium.crypto_secretbox_NONCEBYTES);

  const keyBuffer = toKeyBuffer(organizationSecret);

  const plaintextBuffer = Buffer.alloc(cipherBuffer.length - sodium.crypto_secretbox_MACBYTES);
  if (!sodium.crypto_secretbox_open_easy(plaintextBuffer, cipherBuffer, nonceBuffer, keyBuffer)) {
    return new DecryptionFailed();
  }

  return plaintextBuffer.toString();
}

next()
        return
      }

      const cipher = Buffer.from(cyphertextB64, 'base64')
      const nonce = Buffer.from(nonceB64, 'base64')

      if (cipher.length < sodium.crypto_secretbox_MACBYTES) {
        // not long enough
        request.session = new Session({})
        next()
        return
      }

      const msg = Buffer.allocUnsafe(cipher.length - sodium.crypto_secretbox_MACBYTES)
      if (!sodium.crypto_secretbox_open_easy(msg, cipher, nonce, key)) {
        // unable to decrypt
        request.session = new Session({})
        next()
        return
      }

      request.session = new Session(JSON.parse(msg))
      next()
    })

exports.decrypt = function (cipher, nonce, key) {
  if (cipher.length < sodium.crypto_secretbox_MACBYTES) return null
  var msg = Buffer.alloc(cipher.length - sodium.crypto_secretbox_MACBYTES)
  if (!sodium.crypto_secretbox_open_easy(msg, cipher, nonce, key)) return null
  return msg
}

exports.decrypt = function (cipher, nonce, key) {
  if (cipher.length < sodium.crypto_secretbox_MACBYTES) return null
  var msg = new Buffer(cipher.length - sodium.crypto_secretbox_MACBYTES)
  if (!sodium.crypto_secretbox_open_easy(msg, cipher, nonce, key)) return null
  return msg
}