XBOOT: Free-XOR Gates for CKKS with Applications to Transciphering

This is the code for our work in CHES 2025, named XBOOT: Free-XOR Gates for CKKS with Applications to Transciphering.
Our implementation is based on the Open-sourced FHE library Lattigo v6.0 [1].

Golang installation and configuration

Downloading the latest version of go binary distribution:

wget https://go.dev/dl/go1.24.4.linux-amd64.tar.gz

Delete the existing Golang, and unzip the downloaded file into the environment:

sudo rm -rf /usr/local/go        # delete old version if exists
sudo tar -C /usr/local -xzf go1.24.4.linux-amd64.tar.gz

Editing the shell file and adding the following command (if not existing):

nano ~/.bashrc
export PATH=$PATH:/usr/local/go/bin

Saving and enabling:

source ~/.bashrc

General information about the code structure

XBOOT bootstrapping scheme

This part is located at

# Modified EvalMod function
./circuits/ckks/mod1
# New bootstrapping function added
./circuits/ckks/bootstrapping
# The EvalMod f_bin interpolation function
./utils/cosine/cosine_approx.go

XBOOT based transciphering scheme

We implement the XBOOT transcipering in ./ckks_cipher/, which contains the following functionalities.

• Evaluation of the AES-CTR in the CKKS scheme
• Evaluation of the Rasta-CTR in the CKKS scheme

Application subsequent transciphering

We implement the GAWS chisqtest in ./chisqtest/, which contains the following functionalities.

• chisq test scheme (located at (./chisq.go))

Example containing

An example of Running GWAS chisqtest subsequent XBOOT transciphering is given in ./examples/chisq/main.go.

An example of Running XBOOT-AES transciphering is given in ./examples/transcipher/main.go.

Compile and Run XBOOT

A proof of concept unsecure toy case for AES-CKKS transciphering

cd ./examples/transcipher/main.go
go run main.go --mode=test

Benchmark the AES-CKKS transiphering

Ensure you have sufficient RAM (approximately 64GB) and 64 physical CPU cores for improved parallelization.

cd ./examples/transcipher/main.go
go run main.go --mode=benchmark

Paper

For a detailed description of the framework, please refer to our paper:

Chao Niu, Zhicong Huang, Zhaomin Yang, Yi Chen, Liang Kong, Cheng Hong and Tai Wei. 2025. XBOOT: Free-XOR Gates for CKKS with
Applications to Transciphering IACR Transactions on Cryptographic Hardware and Embedded Systems, 2025(4), xx-xx. [Link] [DOI]

References

[1] "Lattigo v6" Online: https://github.com/tuneinsight/lattigo Aug, 2024.

Disclaimer

The client-side symmetric encryption function and the FHE key schedule evaluation are not currently included.

License

Lattigo is licensed under the Apache 2.0 License. See LICENSE.