Files
ml-sdk/docs/explanations/security_and_correctness.md
zeekay 531fc57003 chore(brand): purge Zama refs across docs, README, configs — phase 1
Brand-only sweep. Touches READMEs, docs, package metadata, comments,
notebook markdown, requirements.txt files; does NOT yet touch Python
`concrete.*` imports (those are module-level dependencies requiring the
phase-2 Python module port from `concrete` → `torus`).

Substitutions applied:

  Concrete ML                  → TorusML
  concrete-ml                  → torus-ml
  Concrete-ML                  → Torus-ML
  concrete_ml                  → torus_ml
  zama-ai/concrete-ml          → luxfhe/ml-sdk
  zama-ai/concrete             → luxfhe/torus
  github.com/zama-ai           → github.com/luxfhe
  docs.zama.ai/concrete-ml     → docs.luxfhe.com/ml-sdk
  docs.zama.ai/concrete        → docs.luxfhe.com/torus
  Zama Concrete ML             → Lux TorusML
  Zama Concrete                → Lux Torus
  Zama tfhe-rs / Zama TFHE-rs  → Lux-FHE
  tfhe-rs / TFHE-rs            → Lux-FHE
  Zama fhEVM / fhEVM           → TorusEVM
  Concrete framework           → Torus framework
  Concrete compiler            → Torus compiler
  Concrete by Zama             → Torus by Lux
  the Zama team                → the Lux Industries team
  Zama's                       → Lux Industries'
  (Zama)                       → (Lux)
  CoFHE / Fhenix               → (removed)

LICENSE: original Zama copyright RETAINED per BSD-3-Clause-Clear §1-§2
requirements; Lux Industries modifications copyright added. Per §3 no
name of ZAMA used to endorse the derived work — product marketed
exclusively as TorusML.

README image URLs migrated to github.com/luxfhe/ml-sdk/assets to break
the dependency on Zama's CDN.

Hit count: 350 → 295. Residual hits are Python `from concrete.fhe import`
imports referencing the upstream Zama `concrete` PyPI package; these
require module-level port (phase 2):

  Phase 2 plan:
    1. Fork zama-ai/concrete (the Python compiler) to luxfhe/torus
    2. Rename Python module `concrete` → `torus`; PyPI publish as `torus-fhe`
    3. Update ml-sdk imports from `concrete.fhe` → `torus.fhe`, etc.
    4. Wire `torus.compiler` GPU dispatch through `luxcpp/gpu` vtbl
       (lux-private/gpu-kernels for CUDA/Metal/WebGPU/FPGA targets)
    5. Port concrete-cuda + concrete-mlir kernels to
       lux-private/gpu-kernels/{cuda,metal,wgsl}/ckks/ (matrix-vector
       mul, rescale, rotate, bootstrap for TorusML inference)

  Phase 3 plan (kernels):
    - CKKS/BGV/BFV GPU kernels in lux-private/gpu-kernels/
      (currently only TFHE PBS / keyswitch / blind-rotate exist)
    - FPGA bitstreams in lux-private/fpga/ (currently scaffold only)

Phase 1 = docs/branding sweep. PR not opened; user reviews and merges.
2026-05-29 13:53:42 -07:00

2.8 KiB

Security and correctness

Security model

The default parameters for TorusML are chosen considering the IND-CPA security model, and are selected with a bootstrapping off-by-one error probability of 2^-40. In particular, it is assumed that the results of decrypted computations are not shared by the secret key owner with any third parties, as such an action can lead to leakage of the secret encryption key. If you are designing an application where decryptions must be shared, you will need to craft custom encryption parameters which are chosen in consideration of the IND-CPA^D security model [1].

Correctness of computations

The cryptography concepts section explains how TorusML can ensure guaranteed correctness of encrypted computations. In this approach, a quantized machine learning model will be converted to an FHE circuit that produces the same result on encrypted data as the original model on clear data.

However, the bootstrapping off-by-one error probability can be configured by the user. Raising this probability results in lower latency when executing on encrypted data, but higher values cancel the correctness guarantee of the default setting. In practice this may not be an issue, as the accuracy of the model may be maintained, even though slight differences are observed in the model outputs. Moreover, as noted in the paragraph above, raising the off-by-one error probability may negatively impact the security model.

Furthermore, a second approach to reduce latency at the expense of correctness is approximate computation of univariate functions. This mode is enabled by using the rounding setting. When using the fhe.Exactness.APPROXIMATE rounding method, off-by-one errors are always induced in the computation of activation functions, irrespective of the bootstrapping off-by-one error probability.

When trading-off better latency for correctness, it is highly recommended to use the FHE simulation feature to measure accuracy on a drawn-out test-set. In many cases the accuracy of the model is only slightly impacted by approximate computations.

References

[1] Li, Baiyu, et al. “Securing approximate homomorphic encryption using differential privacy.” Annual International Cryptology Conference. Cham: Springer Nature Switzerland, 2022. https://eprint.iacr.org/2022/816.pdf