Two-level homomorphic encryption for Node.js by WebAssembly

Abstract

This library supports two kinds of lifted ElGamal encryption,

• which can add two ciphertexts many times, and
• can multiply two ciphertexts once.

For two vectors x = (x1, ..., xn) and y = (y1, ..., yn), EncG1(x1) * EncG2(y1) + ... + EncG1(xn) * EncG2(yn) = EncGT(x1 * y1 + ... + xn * yn).

see mcl

News

• 2026/Sep/12 v2.0.1 Security fixes.
  • Breaking change: enc*, encWithZkp*, mulInt, and verify(c, zkp, m) throw if the plaintext is not an integer in the signed int32 range (NaN, 2.5, '3', 2**31, ...). Previously such values were silently converted by ToInt32 (e.g. encG1(NaN) was Enc(0)).
  • dec fails instead of silently truncating a plaintext beyond int32 when the DLP range is widened by setTryNum.
  • The random function is restored even if enc*(m, randHistory) throws.
  • deserialize rejects an oversized input instead of corrupting the wasm stack.
• 2026/Aug/01 v1.8.0 The wasm module is built with clang instead of emcc.
• 2023/Sep/06 The performance of enc/dec is a little improved.
• 2023/Aug/17 The performance of dec is a little improved.
• 2022/Jul/20 v1.0.0
• 2020/Dec/27 change file layout
• 2020/Dec/18 sec.decWithZkpDec(c, aux) returns [m, zkp] that zkp proves dec(c) = m for CipherTextGT c, and aux.verify(c, zkp, m) returns the correctness where aux = pub.getAuxiliaryForZkpDecGT().
• 2020/Nov/06 sec.decWithZkpDec(c, pub) returns [m, zkp] that zkp proves dec(c) = m for CipherTextG1 c, and pub.verify(c, zkp, m) returns the correctness.

Demo

• cross tabulation demo (switch en/ja by the top-right button)

for Node.js

pnpm test

How to use

The version v0.7.0 breaks backward compatibility of the entry point.

• Node.js : const she = require('she-wasm')
• React : const she = require('she-wasm/browser')
• HTML : <script src="https://herumi.github.io/she-wasm/browser/she.js"></script>

Doc

• Efficient Two-level Homomorphic Encryption in Prime-order Bilinear Groups and A Fast Implementation in WebAssembly, N. Attrapadung, G. Hanaoka, S. Mitsunari, Y. Sakai, K. Shimizu, and T. Teruya. ASIACCS 2018
• slide for ASIA CCS 2018 in English
• slide for SCIS 2018 in Japanese
• she-api
• she-api(Japanese)

How to build

Install Clang and lld.

sudo apt install clang lld
pnpm install
git submodule update --init --recursive
cd src
make

License

modified new BSD License http://opensource.org/licenses/BSD-3-Clause

Author

MITSUNARI Shigeo([email protected])

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