# Library Questions **URL:** https://openfhe.discourse.group/c/user-questions/17.md [Latest](https://openfhe.discourse.group/latest.md) · [Categories](https://openfhe.discourse.group/categories.md) · [Tags](https://openfhe.discourse.group/tags.md) --- ## [About the Library Questions category](https://openfhe.discourse.group/t/about-the-library-questions-category/26)
**Author:** [@iquah](https://openfhe.discourse.group/u/iquah)\ **Replies:** 0
Use this category to ask questions, to report bugs or to post feature requests --- ## [Interested in implementing the CMT FBT large LUT evaluation method](https://openfhe.discourse.group/t/interested-in-implementing-the-cmt-fbt-large-lut-evaluation-method/2387)
**Author:** [@Ishan](https://openfhe.discourse.group/u/Ishan)\ **Replies:** 0\ **Last updated:** [September 23, 2026, 2:52am UTC](https://openfhe.discourse.group/t/interested-in-implementing-the-cmt-fbt-large-lut-evaluation-method/2387 "2026-09-23T02:52:45Z")
Hi, Came across issue #1228 and after reading the paper ( Evaluating Larger Lookup Tables using CKKS ) for the last week, I am interested in implementing the CMT FBT method for LUT evaluation. I have also been going th… --- ## [Policy for finding bugs in the repository](https://openfhe.discourse.group/t/policy-for-finding-bugs-in-the-repository/2371)
**Author:** [@marcos](https://openfhe.discourse.group/u/marcos)\ **Replies:** 1\ **Last updated:** [September 8, 2026, 3:54pm UTC](https://openfhe.discourse.group/t/policy-for-finding-bugs-in-the-repository/2371 "2026-09-08T15:54:29Z")
I was thinking about casually pointing my agents for finding bugs in the repository. Is there a policy or guidelines on how to do this? --- ## [CKKS ReKeyGen throws mismatched RingDimension for Keys of the same CryptoContext using the Python wrapper](https://openfhe.discourse.group/t/ckks-rekeygen-throws-mismatched-ringdimension-for-keys-of-the-same-cryptocontext-using-the-python-wrapper/2350)
**Author:** [@McMiTb](https://openfhe.discourse.group/u/McMiTb)\ **Replies:** 4\ **Last updated:** [August 12, 2026, 9:39pm UTC](https://openfhe.discourse.group/t/ckks-rekeygen-throws-mismatched-ringdimension-for-keys-of-the-same-cryptocontext-using-the-python-wrapper/2350 "2026-08-12T21:39:40Z")
Hello, I want to do a Proxy ReEncryption using the CKKS scheme with the official OpenFHE python wrapper. However, whenever I try to call the ReKeyGen() method I either get a RingDimension mismatch followed by a SIGABRT … --- ## [Serialization: Overview](https://openfhe.discourse.group/t/serialization-overview/2339)
**Author:** [@tomfi](https://openfhe.discourse.group/u/tomfi)\ **Replies:** 2\ **Last updated:** [August 3, 2026, 7:00pm UTC](https://openfhe.discourse.group/t/serialization-overview/2339 "2026-08-03T19:00:46Z")
Hello everyone, I have question regarding serialization of OpenFHE objects. We (@tomfi, @sloede ) are currently implementing serialization in SecureArithmetic.jl / Openfhe.jl. But our current implementation seems unnec… --- ## [Coeffs polynomial mult in CKKS](https://openfhe.discourse.group/t/coeffs-polynomial-mult-in-ckks/2349)
**Author:** [@narger](https://openfhe.discourse.group/u/narger)\ **Replies:** 1\ **Last updated:** [August 3, 2026, 6:40pm UTC](https://openfhe.discourse.group/t/coeffs-polynomial-mult-in-ckks/2349 "2026-08-03T18:40:28Z")
Hi all! I have a question about polynomial mult in CKKS. in particular I’d have to multiply two plaintexts p, \\hat{p} to obtain p \\cdot \\hat{p} \\bmod \\mathbb{Z}\[X\]/(X^N+1), not in slot-wise. As far as I am aware this c… --- ## [Performance regression from v1.4.0 to v1.5.1](https://openfhe.discourse.group/t/performance-regression-from-v1-4-0-to-v1-5-1/2338)
**Author:** [@adriannic](https://openfhe.discourse.group/u/adriannic)\ **Replies:** 1\ **Last updated:** [July 6, 2026, 10:55pm UTC](https://openfhe.discourse.group/t/performance-regression-from-v1-4-0-to-v1-5-1/2338 "2026-07-06T22:55:35Z")
Solved by pull request #1213 Benchmarks used: GitHub - adriannic/openfhe-bench: Personal benchmark suite for openfhe · GitHub Benchmark results: OpenFHE Benchmarks - Google Sheets While running benchmarks to make a pe… --- ## [Ring-switching in CKKS](https://openfhe.discourse.group/t/ring-switching-in-ckks/2337)
**Author:** [@ManhBui](https://openfhe.discourse.group/u/ManhBui)\ **Replies:** 1\ **Last updated:** [July 6, 2026, 10:53pm UTC](https://openfhe.discourse.group/t/ring-switching-in-ckks/2337 "2026-07-06T22:53:02Z")
Hi OpenFHE team, I am currently exploring CKKS implementations for privacy-preserving inference of large foundation models, especially Transformer/LLM inference. I have a question about whether OpenFHE currently support… --- ## [RAM consumption for CKKS Bootstrapping KeyGen](https://openfhe.discourse.group/t/ram-consumption-for-ckks-bootstrapping-keygen/2328)
**Author:** [@Amaiafm](https://openfhe.discourse.group/u/Amaiafm)\ **Replies:** 3\ **Last updated:** [June 18, 2026, 2:51pm UTC](https://openfhe.discourse.group/t/ram-consumption-for-ckks-bootstrapping-keygen/2328 "2026-06-18T14:51:48Z")
Hi everyone, I am using OpenFHE via Python and trying to approximate the RAM consumption during EvalBootstrapKeyGen(). The cryptocontext I am using is CKKS. Memory usage is the most critical factor for my current projec… --- ## [\[Potential Bug Report\] Two potential FIXEDMANUAL bugs in CKKS (bootstrap nsd, EvalLinearWSumMutable crash)](https://openfhe.discourse.group/t/potential-bug-report-two-potential-fixedmanual-bugs-in-ckks-bootstrap-nsd-evallinearwsummutable-crash/2326)
**Author:** [@BurakK](https://openfhe.discourse.group/u/BurakK)\ **Replies:** 1\ **Last updated:** [June 9, 2026, 6:52pm UTC](https://openfhe.discourse.group/t/potential-bug-report-two-potential-fixedmanual-bugs-in-ckks-bootstrap-nsd-evallinearwsummutable-crash/2326 "2026-06-09T18:52:59Z")
Hi all, I ran into two issues with FIXEDMANUAL that I believe may be bugs, but I’d like confirmation before opening GitHub issues. Tested on a recent dev clone (commit hash 6ba41303), and main clone (commit hash ed361af… --- ## [Multiparty sceheme switching non probibalistic?](https://openfhe.discourse.group/t/multiparty-sceheme-switching-non-probibalistic/2325)
**Author:** [@ctgryt](https://openfhe.discourse.group/u/ctgryt)\ **Replies:** 1\ **Last updated:** [June 8, 2026, 3:25pm UTC](https://openfhe.discourse.group/t/multiparty-sceheme-switching-non-probibalistic/2325 "2026-06-08T15:25:16Z")
Hello, my question is regarding whether there exists a method or set of parameters in this library that allow a client and server to compare two values and return true or false. The use case is a follows. A server holds… --- ## [FFT on ciphertexts](https://openfhe.discourse.group/t/fft-on-ciphertexts/2320)
**Author:** [@Lena](https://openfhe.discourse.group/u/Lena)\ **Replies:** 1\ **Last updated:** [May 26, 2026, 4:44pm UTC](https://openfhe.discourse.group/t/fft-on-ciphertexts/2320 "2026-05-26T16:44:30Z")
Is there an implementation in OpenFHE that performs FFT on ciphertexts? --- ## [RFC: branch-free modular primitives on the decrypt path (constant-time hardening)](https://openfhe.discourse.group/t/rfc-branch-free-modular-primitives-on-the-decrypt-path-constant-time-hardening/2316)
**Author:** [@bader](https://openfhe.discourse.group/u/bader)\ **Replies:** 2\ **Last updated:** [April 29, 2026, 8:14pm UTC](https://openfhe.discourse.group/t/rfc-branch-free-modular-primitives-on-the-decrypt-path-constant-time-hardening/2316 "2026-04-29T20:14:58Z")
Hi all, I've prepared a constant-time hardening of the modular primitives. Data-dependent branches are replaced with bitmask-select plus a compiler barrier that survives \`-O0..-Ofast\` on GCC and Clang. ## Branch http… --- ## [BFV Plaintext Modulus](https://openfhe.discourse.group/t/bfv-plaintext-modulus/2315)
**Author:** [@fishr](https://openfhe.discourse.group/u/fishr)\ **Replies:** 1\ **Last updated:** [April 29, 2026, 6:45pm UTC](https://openfhe.discourse.group/t/bfv-plaintext-modulus/2315 "2026-04-29T18:45:54Z")
Hello everyone, I’m currently struggling with understanding why my ciphertexts are not decrypting correctly. The library API does not report any errors. Here is the minimal example: #include \ using namespa… --- ## [Implement CKKS- coefficient encoding multiplication](https://openfhe.discourse.group/t/implement-ckks-coefficient-encoding-multiplication/2164)
**Author:** [@sihyeok](https://openfhe.discourse.group/u/sihyeok)\ **Replies:** 3\ **Last updated:** [April 29, 2026, 4:49pm UTC](https://openfhe.discourse.group/t/implement-ckks-coefficient-encoding-multiplication/2164 "2026-04-29T16:49:28Z")
I want to implement an inner product using CKKS coefficient encoding (i.e., encode vectors as polynomial coefficients, multiply polynomials, and extract the relevant coefficient). Furthermore, I want to implement them i… --- ## [Understanding CKKS precision limits for large magnitude values](https://openfhe.discourse.group/t/understanding-ckks-precision-limits-for-large-magnitude-values/2313)
**Author:** [@Claire](https://openfhe.discourse.group/u/Claire)\ **Replies:** 1\ **Last updated:** [April 22, 2026, 3:41pm UTC](https://openfhe.discourse.group/t/understanding-ckks-precision-limits-for-large-magnitude-values/2313 "2026-04-22T15:41:59Z")
Hello, I am trying to understand the practical limitations on double-precision values when using CKKS. In standard 64-bit floating-point arithmetic, we have a 52-bit mantissa. However, in CKKS, due to ciphertext repres… --- ## [Suggestion on error message](https://openfhe.discourse.group/t/suggestion-on-error-message/2312)
**Author:** [@narger](https://openfhe.discourse.group/u/narger)\ **Replies:** 2\ **Last updated:** [April 17, 2026, 1:22pm UTC](https://openfhe.discourse.group/t/suggestion-on-error-message/2312 "2026-04-17T13:22:41Z")
Hi developers, i open a thread here as i can not open an issue in github I’d like to suggest a minor change to the library which might help users. In particular, when one tries to evaluate a rotation in CKKS without fir… --- ## [Modulus mismatch in EvalCKKStoFHEW after KeySwitch from reconstructed ciphertext](https://openfhe.discourse.group/t/modulus-mismatch-in-evalckkstofhew-after-keyswitch-from-reconstructed-ciphertext/2308)
**Author:** [@Mosi](https://openfhe.discourse.group/u/Mosi)\ **Replies:** 1\ **Last updated:** [April 9, 2026, 5:41pm UTC](https://openfhe.discourse.group/t/modulus-mismatch-in-evalckkstofhew-after-keyswitch-from-reconstructed-ciphertext/2308 "2026-04-09T17:41:22Z")
Hi, I am implementing a pipeline where a ciphertext is generated externally, reconstructed in OpenFHE by manually setting its polynomial elements and metadata, KeySwitched to a server key, multiplied twice by a scalar, … --- ## [OpenFHE CKKS chooses modulus chain that doesn't guarantee 128 bits of security](https://openfhe.discourse.group/t/openfhe-ckks-chooses-modulus-chain-that-doesnt-guarantee-128-bits-of-security/405)
**Author:** [@hilder](https://openfhe.discourse.group/u/hilder)\ **Replies:** 14\ **Last updated:** [April 8, 2026, 2:26am UTC](https://openfhe.discourse.group/t/openfhe-ckks-chooses-modulus-chain-that-doesnt-guarantee-128-bits-of-security/405 "2026-04-08T02:26:20Z")
I slightly changed the advanced CKKS example by replacing the ring dimension and the security level by parameters.SetRingDim(1 \<\< 16); parameters.SetSecurityLevel(HEStd\_128\_classic); Since I chose the security level as… --- ## [\[Bug report\]BFV EvalAdd produces incorrect results when ciphertexts have mismatched DCRTPoly formats (EVALUATION vs COEFFICIENT)](https://openfhe.discourse.group/t/bug-report-bfv-evaladd-produces-incorrect-results-when-ciphertexts-have-mismatched-dcrtpoly-formats-evaluation-vs-coefficient/2304)
**Author:** [@WayneOnEarth](https://openfhe.discourse.group/u/WayneOnEarth)\ **Replies:** 1\ **Last updated:** [March 25, 2026, 4:56pm UTC](https://openfhe.discourse.group/t/bug-report-bfv-evaladd-produces-incorrect-results-when-ciphertexts-have-mismatched-dcrtpoly-formats-evaluation-vs-coefficient/2304 "2026-03-25T16:56:00Z")
Summary When using EvalMultNoRelin in BFV to produce a 3-element ciphertext (vital for lazy relinearization related research), the resulting ciphertext’s DCRTPoly elements are in COEFFICIENT format. However, freshly encr… --- ## [Polynomial representation of ciphertext from MakeCoefPackedPlaintext](https://openfhe.discourse.group/t/polynomial-representation-of-ciphertext-from-makecoefpackedplaintext/2303)
**Author:** [@krist](https://openfhe.discourse.group/u/krist)\ **Replies:** 2\ **Last updated:** [March 21, 2026, 8:24am UTC](https://openfhe.discourse.group/t/polynomial-representation-of-ciphertext-from-makecoefpackedplaintext/2303 "2026-03-21T08:24:34Z")
When encrypting a plaintext from MakeCoefPackedPlaintext does the resulting ciphertext use Poly, NativePoly or DCRTPoly to represent it? Or something else entirely? If it makes a difference I am using the Python version … --- ## [Impact of ScalingModSize and/or FirstModSIze choices](https://openfhe.discourse.group/t/impact-of-scalingmodsize-and-or-firstmodsize-choices/2302)
**Author:** [@krist](https://openfhe.discourse.group/u/krist)\ **Replies:** 2\ **Last updated:** [March 21, 2026, 8:23am UTC](https://openfhe.discourse.group/t/impact-of-scalingmodsize-and-or-firstmodsize-choices/2302 "2026-03-21T08:23:35Z")
Are computations for faster for lower values ScalingModSize and/or FirstModeSize? Or is it generally better to use the highest values allowed for a particular ring dimension? Also, does the values of ScalingModSize and/… --- ## [Installation issue: module not found](https://openfhe.discourse.group/t/installation-issue-module-not-found/2290)
**Author:** [@helen](https://openfhe.discourse.group/u/helen)\ **Replies:** 3\ **Last updated:** [March 19, 2026, 2:28pm UTC](https://openfhe.discourse.group/t/installation-issue-module-not-found/2290 "2026-03-19T14:28:21Z")
I’m trying to install openfhe-python with pip and keep getting the following error: ModuleNotFoundError: No module named ‘openfhe.openfhe’. I’ve tried installing it with macOS/pip and with docker/pip. I’m using 3.14 with… --- ## [Using NOISE\_FLOODING\_DECRYPT for CKKS in a multiparty setting](https://openfhe.discourse.group/t/using-noise-flooding-decrypt-for-ckks-in-a-multiparty-setting/2297)
**Author:** [@krist](https://openfhe.discourse.group/u/krist)\ **Replies:** 5\ **Last updated:** [March 13, 2026, 9:06am UTC](https://openfhe.discourse.group/t/using-noise-flooding-decrypt-for-ckks-in-a-multiparty-setting/2297 "2026-03-13T09:06:45Z")
Hello. I am trying to use the NOISE\_FLOODING\_DECRYPT mode for CKKS in a multiparty setting in the Python version of OpenFHE. This post Support for NOISE\_FLOODING\_MULTIPARTY in threshold CKKS? - Library Questions - Open… --- ## [Coef encoding vs CRT encoding](https://openfhe.discourse.group/t/coef-encoding-vs-crt-encoding/2300)
**Author:** [@krist](https://openfhe.discourse.group/u/krist)\ **Replies:** 2\ **Last updated:** [March 12, 2026, 6:51pm UTC](https://openfhe.discourse.group/t/coef-encoding-vs-crt-encoding/2300 "2026-03-12T18:51:53Z")
Hello. I have been watching webinars Homomorphic Encryption for OpenFHE Users – OpenFHE.org and reading forum posts such as Ressources for Batching, but I am wondering if my understanding is correct. For coef encoding,… --- ## [Possible values for ScalingModSize in BFV](https://openfhe.discourse.group/t/possible-values-for-scalingmodsize-in-bfv/2294)
**Author:** [@krist](https://openfhe.discourse.group/u/krist)\ **Replies:** 2\ **Last updated:** [March 10, 2026, 10:48am UTC](https://openfhe.discourse.group/t/possible-values-for-scalingmodsize-in-bfv/2294 "2026-03-10T10:48:20Z")
Hello. I am trying to use BFV for encrypting vectors which can contain values \\{-1, 0, 1\\}. The use case is for multiparty with 3 Clients. The Version being used in the Python wrapper. I have been experimenting with di… --- ## [OpenMP vs alternatives](https://openfhe.discourse.group/t/openmp-vs-alternatives/2281)
**Author:** [@j2kun](https://openfhe.discourse.group/u/j2kun)\ **Replies:** 1\ **Last updated:** [March 2, 2026, 1:02pm UTC](https://openfhe.discourse.group/t/openmp-vs-alternatives/2281 "2026-03-02T13:02:28Z")
Over at the HEIR project, support for OpenMP has been a recurring obstacle for us. For exmaple, Google internally does not support OpenMP, nor does Apple clang, compiling with OpenMP in bazel breaks hermeticity, it compl… --- ## [Modulus switching in openfhe-python](https://openfhe.discourse.group/t/modulus-switching-in-openfhe-python/2279)
**Author:** [@NJay](https://openfhe.discourse.group/u/NJay)\ **Replies:** 1\ **Last updated:** [March 2, 2026, 12:48pm UTC](https://openfhe.discourse.group/t/modulus-switching-in-openfhe-python/2279 "2026-03-02T12:48:16Z")
Hello, I have a question about the modulus switching in CKKS, and I’m using openFHE-python. To add two ciphertexts that have different levels (e.g., level L and L-1), I’d like to reduce only the level L to L-1. But Mod… --- ## [Inconsistent minimum value for scalingModSize](https://openfhe.discourse.group/t/inconsistent-minimum-value-for-scalingmodsize/2278)
**Author:** [@hyerinpark](https://openfhe.discourse.group/u/hyerinpark)\ **Replies:** 1\ **Last updated:** [March 2, 2026, 12:25pm UTC](https://openfhe.discourse.group/t/inconsistent-minimum-value-for-scalingmodsize/2278 "2026-03-02T12:25:26Z")
Hello, I noticed a potential inconsistency regarding the minimum allowed value of scalingModSize. In commit 2052e64, the following condition checking and exception message was introduced in src/pke/lib/scheme/gen-crypt… --- ## [Serialize and Deserialize SchemeSwitching in openfhe-python](https://openfhe.discourse.group/t/serialize-and-deserialize-schemeswitching-in-openfhe-python/2277)
**Author:** [@div](https://openfhe.discourse.group/u/div)\ **Replies:** 1\ **Last updated:** [March 2, 2026, 12:18pm UTC](https://openfhe.discourse.group/t/serialize-and-deserialize-schemeswitching-in-openfhe-python/2277 "2026-03-02T12:18:49Z")
Dear Team, For the scheme-switching.py example mentioned on the github repository of openfhe python, I want to replicate it in form of client server environment. This requires serialization. Now I have serialized crypto… [Next page](https://openfhe.discourse.group/c/user-questions/17.md?page=1)