> ## Documentation Index > Fetch the complete documentation index at: https://docs.thistle.tech/llms.txt > Use this file to discover all available pages before exploring further. # Get Started: AI Model Update, End-to-end Encrypted Model > End-to-end encryption for AI models with Thistle OTA Per-file encryption (PFE) allows AI model files to be encrypted individually before delivery, so that they remain encrypted in transit, and at rest on the device, until an application explicitly decrypts them. This guide walks you through the steps to * encrypt and publish an AI model file using Thistle Release Helper (TRH), and * fetch the encrypted AI model file and decrypt it on-device using Thistle Update Client (TUC) ## Tools needed * Version 1.8.0 (or above) of TUC and TRH for your platform * The [Thistle Update Client](/binaries#thistle-update-client-tuc): A binary to run on the device side to obtain the latest OTA update * The [Thistle Release Helper](/binaries#release-helper-trh): A CLI developer tool to prepare and publish OTA releases * One may also try out TUC and TRH on a web browser using [Thistle OTA update demo](https://demo.thistle.tech) * On the [Thistle Control Center App](https://app.thistle.tech/projects). Visit the settings section of a project to obtain the API token ("Project Access Token") to be used as `THISTLE_TOKEN` in the configuration step below. Project's Access Token In "Settings > General > Project Configuration", make sure the "Encrypted OTA" feature is on. Encrypted OTA Configuration ## TRH configuration and initialization Configure your Thistle project's access token for TRH ```bash theme={"dark"} $ export THISTLE_TOKEN=$(cat) (paste access token, press enter, then ctrl-d) $ ./trh --signing-method="remote" init ``` ```powershell theme={"dark"} # Set up your project's access token - Windows PowerShell $ $env:THISTLE_TOKEN = "[Access Token Obtained from Thistle App's Project Settings section]" $ .\trh.exe --signing-method="remote" init ``` Here, we first initialize the local working environment by executing the `trh init` command. This creates a Cloud-KMS-backed key pair on the Thistle backend; if a key pair already exists on the backend, the public key portion is returned. The private key in the key pair is used to sign the OTA update bundle and encrypt AI model files. An OTA update manifest file template `manifest.json` is also created locally in the current directory. Your local working environment is now ready. ## Prepare and release an encrypted AI model file Package an OTA update bundle containing a dummy AI model file, `model.pt`, which will be installed in encrypted form at path `/tmp/ota/pfe-install/model.pt.thistlepfe` on a device. ```bash theme={"dark"} $ mkdir -p ota_release # Create a dummy AI model file for demonstration $ echo "This is a dummy PyTorch AI model file" > ota_release/model.pt # Note the --encrypt-ai-model flag $ trh --signing-method="remote" prepare \ --target="ota_release" \ --file-base-path="/tmp/ota/pfe-install/" \ --encrypt-ai-model ``` When the `--encrypt-ai-model` flag is present, `trh prepare` iterates over all files under the target release directory and encrypts each file to produce a per-file encrypted (PFE) artifact with the `.thistlepfe` extension. In our case, `ota_release/model.pt` is encrypted as `ota_release/model.pt.thistlepfe`, which will be delivered and stored on-device at `/tmp/ota/pfe-install/model.pt.thistlepfe`. ## Publish the encrypted AI model file for OTA update Release the prepared OTA update bundle including the encrypted AI model file to Thistle backend. ```bash theme={"dark"} trh --signing-method="remote" release ``` ## Get encrypted AI model file with TUC Create a TUC configuration file `tuc-config.json` for a device. ```bash theme={"dark"} $ trh --signing-method="remote" gen-device-config \ --device-name="encrypted-ai-model-demo-device" \ --enrollment-type="pre-enroll" \ --persist="/tmp/ota" \ --config-path="./tuc-config.json" ``` Put the generated `tuc-config.json` on a device where `tuc` is run to receive the encrypted AI model. In this guide, we will run `tuc` on the same machine where `trh` is run. ```bash theme={"dark"} $ tuc --log-level info -c tuc-config.json & ``` When the OTA update finishes successfully, you should see the encrypted AI model file at path `/tmp/ota/pfe-install/model.pt.thistlepfe`. The file remains encrypted on the device until explicitly decrypted. ## Decrypt AI model on device To decrypt the AI model file for use, an application calls `tuc` with the `decrypt-file` subcommand, supplying the encrypted file path and the desired output path. ```bash theme={"dark"} $ mkdir -p /tmp/decrypted $ tuc -c tuc-config.json decrypt-file \ /tmp/ota/pfe-install/model.pt.thistlepfe \ /tmp/decrypted/model.pt .. Device id: 1fe727a68b07e852a60a366d422e43be !! Thistle client starting up - version 1.8.0 .. success ``` The application can then load the decrypted model from `/tmp/decrypted/model.pt`. ## Combining with other flags The `--encrypt-ai-model` flag can be combined with other `trh prepare` flags: * **Encrypted OTA** (`--encrypt-ota --zip-target`): Encrypts the entire OTA bundle in transit and in the cloud, while also per-file encrypting each AI model at rest on the device. * **AI model signing** (`--sign-ai-model`): When both `--encrypt-ai-model` and `--sign-ai-model` are present, the signature is generated for the encrypted AI model file (the `.thistlepfe` artifact). For example, to combine all three: ```bash theme={"dark"} $ trh --signing-method="remote" prepare \ --target="ota_release" \ --file-base-path="/tmp/ota/pfe-install/" \ --encrypt-ai-model \ --sign-ai-model \ --encrypt-ota --zip-target ``` ## More options In this get started guide, we explained the usage of the Thistle Update Client alongside the Thistle Release Helper to deliver per-file encrypted AI models - and many more use cases are supported! * [File update](/update/get_started/file_update) * [AI model update, with provenance](/update/get_started/ai_model_update_signed_model) * [Encrypted OTA update](/update/get_started/encrypted_ota_file_update) * [A/B tested Raspberry Pi 4 update support](/hardware/raspberry_pi/rpi4_ota_ab_update) * Support for pre & post install scripts * OTA bundle signing using external signing tools * [With YubiKey-protected signing key](https://github.com/thistletech/trh-y) * [With GCP-KMS-backed signing key](https://github.com/thistletech/trh-k)