SpiceCrypt – Open‑Source Python Library for Decrypting LTspice Encrypted Model Files

SpiceCrypt: The Open‑Source Python Library That Unlocks Encrypted LTspice Models

SpiceCrypt is a lightweight, pure‑Python library that decrypts LTspice® encrypted model files, enabling circuit‑simulation engineers to reuse third‑party SPICE models across any simulator.

What Is SpiceCrypt?

LTspice has become the de‑facto standard for analog circuit simulation, but many commercial model vendors ship their SPICE models in a proprietary encrypted format (.CIR, .SUB). This encryption deliberately locks the model to LTspice, preventing reuse in open‑source tools such as NGSpice or PySpice. SpiceCrypt changes that landscape by providing a reliable, legally‑compliant way to decrypt those files on the fly.

The project is hosted on GitHub, released under the GNU AGPL‑3.0 license, and requires only Python 3.10+ with zero external dependencies. Its dual‑format support—text‑based DES‑style encryption and a binary XOR‑stream cipher—covers virtually every encrypted model you’ll encounter in the wild.

Key Features and Capabilities

• Automatic format detection: SpiceCrypt inspects the file header and selects the appropriate decryption routine without user intervention.
• Command‑line interface (CLI): A single spice-decrypt command handles file‑to‑file, stdout, and raw‑hex conversions.
• Python API: Functions like decrypt() and decrypt_stream() let developers embed decryption directly into custom workflows.
• Verification values: CRC‑based checksums (or CRC‑32 for binary files) are returned to guarantee integrity after decryption.
• No third‑party libraries: The library is pure Python, making installation trivial on any platform.
• Cross‑platform support: Works on Windows, macOS, and Linux without modification.

Why LTspice Users Should Care

For circuit‑simulation engineers, the ability to access encrypted models unlocks several strategic advantages:

1. Interoperability: Use the same model in LTspice, NGSpice, or any Python‑based simulator, ensuring consistent results across design stages.
2. Cost efficiency: Avoid purchasing multiple licenses for different simulators when a single decrypted model suffices.
3. Rapid prototyping: Integrate decrypted models into automated test benches powered by Workflow automation studio or custom Python scripts.
4. Future‑proofing: Preserve valuable vendor models even if LTspice’s licensing terms change.

How to Install and Use the Python Library

Installation is a one‑liner with uv, the modern Python package manager:

uv tool install git+https://github.com/jtsylve/spice-crypt.git

Alternatively, add it as a dependency to an existing project:

uv add git+https://github.com/jtsylve/spice-crypt.git

Command‑Line Example

# Decrypt to a new file
spice-decrypt -o mymodel.cir encrypted_model.CIR

# Show verification values
spice-decrypt --verbose encrypted_model.CIR

# Decrypt raw hex data (non‑LTspice format)
spice-decrypt --raw hex_dump.txt

Python API Example

from spice_crypt import decrypt, decrypt_stream

# Decrypt a file and capture verification data
plaintext, (crc1, crc2) = decrypt_stream("encrypted_model.CIR")
print(plaintext)

# Stream‑decrypt directly to another file
_, verification = decrypt_stream("encrypted_model.CIR", "decrypted.cir")
print("Verification:", verification)

The API returns both the decrypted text and a tuple of verification values, allowing you to embed integrity checks into CI pipelines or automated simulation suites.

Open‑Source Nature and Community Support

SpiceCrypt lives on GitHub where contributors continuously improve format support and documentation. The project follows a transparent development model:

• All code is reviewed via pull requests, ensuring high quality and security.
• Issues are triaged weekly, with a focus on compatibility with the latest LTspice releases.
• Comprehensive SPECIFICATION.md explains the cryptographic details, satisfying legal exemptions for interoperability under U.S. 17 U.S.C.§ 1201(f) and EU Software Directive 2009/24/EC.

By joining the community, you can contribute new decryption heuristics, add support for emerging file signatures, or simply share your success stories on the UBOS portfolio examples page.

Take the Next Step – Integrate SpiceCrypt with UBOS

If you’re already leveraging UBOS for AI‑driven automation, SpiceCrypt can become a powerful addition to your workflow. Here’s how you can combine the two platforms:

• Use the Web app editor on UBOS to build a UI that uploads encrypted LTspice files, runs spice-decrypt in the backend, and returns the plaintext model for downstream analysis.
• Automate batch decryption with the Workflow automation studio, chaining SpiceCrypt to your simulation pipelines.
• Expose the decrypted models to AI marketing agents that generate datasheets or marketing copy directly from the model parameters.
• Leverage UBOS templates for quick start such as the AI Article Copywriter to automatically document the model’s behavior after decryption.
• Integrate with the AI Video Generator to produce tutorial videos that walk engineers through the decrypted circuit.
• Deploy a GPT‑Powered Telegram Bot that answers on‑the‑fly questions about the decrypted model, merging the ChatGPT and Telegram integration with SpiceCrypt’s output.

Ready to explore pricing? Check the UBOS pricing plans for a tier that matches your team size, whether you’re a startup (UBOS for startups) or an enterprise (Enterprise AI platform by UBOS).

Conclusion

SpiceCrypt democratizes access to LTspice encrypted models, turning a once‑closed ecosystem into an open, interoperable resource for engineers worldwide. Its pure‑Python implementation, zero‑dependency footprint, and robust CLI/API make it a natural fit for both ad‑hoc decryption and large‑scale automation.

By pairing SpiceCrypt with the versatile tools available on the UBOS homepage, you can build end‑to‑end solutions that span model decryption, AI‑enhanced documentation, and automated deployment—all while staying within legal bounds for interoperability.

“SpiceCrypt is the missing link that lets us reuse premium SPICE models across any simulation environment, saving weeks of development time.” – Senior Analog Design Engineer

Dive into the source code, contribute to the community, and start unlocking encrypted models today. The future of circuit simulation is open—let SpiceCrypt be your key.