Question for Coefficient Packing for CKKS and File Not Found Error in Scheme-Switching branch

Library Questions
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1

Hi, I have a couple of questions related to packing functions and scheme-switching, and I would appreciate your insights and assistance.

First, I am curious about the compatibility of the CoefPackedPlaintext method with the CKKS scheme. Specifically, I am interested in using CoefPackedPlaintext to encode an integer vector into coefficients and perform switching using CKKS-FHEW. If I directly uses that packing in CKKS, it outputs sizeQl error like:
“terminating due to uncaught exception of type lbcrypto::math_error: …/openfhe-development/src/pke/lib/scheme/ckksrns/ckksrns-pke.cpp:63 sizeQl 3!= 1. If sizeQl = 0, consider increasing the depth. If sizeQl > 1, check parameters (this is unsupported for NativePoly).”

Second, I have encountered a “file not found” error while attempting to run the scheme-switching branch. When I try to run my won code calling openfhe, the error occurs like:

In file included from /usr/local/include/openfhe/pke/openfhe.h:54:
/usr/local/include/openfhe/pke/cryptocontext.h:54:10: fatal error: '../../binfhe/include/binfhecontext.h' file not found
#include "../../binfhe/include/binfhecontext.h"
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

Currently I believe there is some changed directory in the branch since it works well if I reinstall the library with main branch.

I’m looking forward to hearing your answers. Thank you for your time in advance!

2

The scheme-switching branch is still under development and is not yet ready for use. We plan to add the CKKS-FHEW scheme switching capability in v1.1.0, which is scheduled to be released by the end of July.

3

Thank you for the information. I’m eagerly looking forward to the release of v1.1!

Regarding my first question about the Coefficient packing method for CKKS, I would like to inquire about its compatibility. The current CoefPackedPlaintext function only supports encoding an int64_t vector. However, I think it is possible in theory to encode integer vector into CKKS. I would greatly appreciate your explanation with current library structure and the reason of above error in decryption. Thanks!

4

Hi @swanhong CoefPackedPlaintext is currently supported only for BGV and BFV (for the case where numbers modulo t are encoded). We have not seen yet a need for a coefficient encoding in CKKS (as a user feature). All use cases we have seen typically work with the CKKSPackedEncoding encoding.

The coefficient encoding internally comes up in CKKS bootstrapping or scheme switching from CKKS ↔ FHEW, but these are handled automatically by the library using methods like SlotsToCoef (still operating on plaintexts encoded with CKKSPackedEncoding) I suggest waiting for the v1.1 release where you will see how scheme switching is done.

5

Thanks @ypolyakov I will definitely be on the lookout for the updated version. Appreciated!