# Security Guarantees and Best Practices for FIXED\_NOISE\_MULTIPARTY vs. NOISE\_FLOODING\_MULTIPARTY **URL:** \ **Category:** Library Questions\ **Created:** [December 17, 2024, 4:34am UTC](https://openfhe.discourse.group/t/security-guarantees-and-best-practices-for-fixed-noise-multiparty-vs-noise-flooding-multiparty/1784 "2024-12-17T04:34:15Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![keiyou](https://avatars.discourse-cdn.com/v4/letter/k/f05b48/32.png) [@keiyou](https://openfhe.discourse.group/u/keiyou)\ **Post date:** [December 17, 2024, 4:34am UTC](https://openfhe.discourse.group/t/security-guarantees-and-best-practices-for-fixed-noise-multiparty-vs-noise-flooding-multiparty/1784/1 "2024-12-17T04:34:15Z")
Hi everyone. I have been working with multiparty BFV and BGV in OpenFHE and noticed that the default setting is `FIXED_NOISE_MULTIPARTY`. My understanding is that this approach uses deterministic (fixed) noise rather than random noise. I have two main questions: 1. Security Guarantees: Does `FIXED_NOISE_MULTIPARTY` still provide basic security guarantees, or is it only intended for reproducibility and debugging rather than real-world security scenarios? In other words, if I use `FIXED_NOISE_MULTIPARTY`, am I sacrificing core security properties? 2. Experimentation: For running experiments, is it sufficient to stick with `FIXED_NOISE_MULTIPARTY`, or is it recommended to use `NOISE_FLOODING_MULTIPARTY` because `FIXED_NOISE_MULTIPARTY` is not considered secure? Any guidance or best practices from the developers or experienced users would be greatly appreciated. Thank you! ---
**Author:** ![ypolyakov](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/ypolyakov/32/47_2.png) [@ypolyakov](https://openfhe.discourse.group/u/ypolyakov)\ **Post date:** [December 18, 2024, 4:25am UTC](https://openfhe.discourse.group/t/security-guarantees-and-best-practices-for-fixed-noise-multiparty-vs-noise-flooding-multiparty/1784/2 "2024-12-18T04:25:37Z")
> [@keiyou](#): > > My understanding is that this approach uses deterministic (fixed) noise rather than random noise. No, it is uses random (Gaussian) noise but the standard deviation of the noise is fixed (at 2^{20}). This provides some security (for a small number of decryption queries, like in the hundreds), but is not generally secure. > [@keiyou](#): > > In other words, if I use `FIXED_NOISE_MULTIPARTY`, am I sacrificing core security properties? Yes. > [@keiyou](#): > > For running experiments, is it sufficient to stick with `FIXED_NOISE_MULTIPARTY`, or is it recommended to use `NOISE_FLOODING_MULTIPARTY` because `FIXED_NOISE_MULTIPARTY` is not considered secure? `NOISE_FLOODING_MULTIPARTY` should be used for all experiments where the number of decryption queries is allowed to be large/arbitrary. ---
**Author:** ![keiyou](https://avatars.discourse-cdn.com/v4/letter/k/f05b48/32.png) [@keiyou](https://openfhe.discourse.group/u/keiyou)\ **Post date:** [December 18, 2024, 7:21am UTC](https://openfhe.discourse.group/t/security-guarantees-and-best-practices-for-fixed-noise-multiparty-vs-noise-flooding-multiparty/1784/3 "2024-12-18T07:21:36Z")
Thank you so much for the clarification! Just to make it more concrete: if I’m performing a relatively small number of decryptions in my experiments (for instance, fewer than 100 times or even fewer than 500), would it still be advisable to switch to `NOISE_FLOODING_MULTIPARTY` for better security? Or in such a constrained scenario, would `FIXED_NOISE_MULTIPARTY` be considered sufficient for the sake of better performance? ---
**Author:** ![ypolyakov](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/ypolyakov/32/47_2.png) [@ypolyakov](https://openfhe.discourse.group/u/ypolyakov)\ **Post date:** [December 19, 2024, 1:56pm UTC](https://openfhe.discourse.group/t/security-guarantees-and-best-practices-for-fixed-noise-multiparty-vs-noise-flooding-multiparty/1784/4 "2024-12-19T13:56:56Z")
For strong security guarantees (related to provable security), it is advised to use `NOISE_FLOODING_MULTIPARTY`. For practical security (if it known that number of possible decryptions is bounded), `FIXED_NOISE_MULTIPARTY` may be sufficient. My suggestion would be to run experiments for both designs and report both numbers at least for some settings. ---
**Author:** ![keiyou](https://avatars.discourse-cdn.com/v4/letter/k/f05b48/32.png) [@keiyou](https://openfhe.discourse.group/u/keiyou)\ **Post date:** [December 20, 2024, 1:13am UTC](https://openfhe.discourse.group/t/security-guarantees-and-best-practices-for-fixed-noise-multiparty-vs-noise-flooding-multiparty/1784/5 "2024-12-20T01:13:16Z")
Thanks for clarifying. I’ll try both modes and report results from each scenario. Your advice is much appreciated. ---
**Author:** ![oksuman](https://avatars.discourse-cdn.com/v4/letter/o/6de8d8/32.png) [@oksuman](https://openfhe.discourse.group/u/oksuman)\ **Post date:** [November 5, 2025, 8:57am UTC](https://openfhe.discourse.group/t/security-guarantees-and-best-practices-for-fixed-noise-multiparty-vs-noise-flooding-multiparty/1784/6 "2025-11-05T08:57:04Z")
Thank you for the helpful information, and sorry for reopening a resolved topic. I just have one more question; is there any theoretical background or reference for the `NOISE_FLOODING_MULTIPARTY` technique? It seems to introduce very large noise (as described in [Threshold\_FHE.md](https://github.com/openfheorg/openfhe-development/blob/main/docs/static_docs/Threshold_FHE.md)), but I couldn’t find any cited sources. Any pointer would be appreciated. Thank you again. ---
**Author:** ![ypolyakov](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/ypolyakov/32/47_2.png) [@ypolyakov](https://openfhe.discourse.group/u/ypolyakov)\ **Post date:** [November 10, 2025, 4:13pm UTC](https://openfhe.discourse.group/t/security-guarantees-and-best-practices-for-fixed-noise-multiparty-vs-noise-flooding-multiparty/1784/7 "2025-11-10T16:13:45Z")
Please create a new topic for this question. Thanks.