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A portable and fast pairing-based cryptography library.


mcl is a library for pairing-based cryptography, which supports the optimal Ate pairing over BN curves and BLS12-381 curves.


  • mclBn_eth* functions are removed.
  • mcl::bn::mapToG1(G1& out, const Fp& v) supports BLS12_MAP_FP_TO_G1 in EIP 2537.
  • mcl::bn::hashAndMapToG1(G1& out, const void *msg, size_t msgSize) supports (hash-to-curve-09 BLS12381G1_XMD:SHA-256_SSWU_RO_)
  • MCL_MAP_TO_MODE_HASH_TO_CURVE_07 is added for hash-to-curve-draft-07.
    • The older version will be removed in the future.
  • change DST of hash-to-curve for MCL_MAP_TO_MODE_HASH_TO_CURVE_06.
  • add new hash-to-curve function of hash-to-curve-draft-06 at March 2020.
    • call setETHmode(MCL_MAP_TO_MODE_HASH_TO_CURVE_06);
    • The older MAP_TO_MODE will be removed after the draft is fixed.
  • add new hash functions corresponding to python-impl of algorand/bls_sig_ref.
    • mclBn_ethMsgToFp2(resp. Hp2)
    • mclBn_ethFp2ToG2(resp. opt_swu2_map)
    • mclBn_ethMsgToG2(resp. map2curve_osswu2)

Support architecture

  • x86-64 Windows + Visual Studio
  • x86, x86-64 Linux + gcc/clang
  • x86-64 macOS
  • ARM / ARM64 Linux
  • WebAssembly
  • Android
  • iPhone
  • (maybe any platform to be supported by LLVM)

Support curves

  • BN curve ; p(z) = 36z^4 + 36z^3 + 24z^2 + 6z + 1.
    • BN254 ; a BN curve over the 254-bit prime p(z) where z = -(2^62 + 2^55 + 1).
    • BN_SNARK1 ; a BN curve over a 254-bit prime p such that n := p + 1 - t has high 2-adicity.
    • BN381_1 ; a BN curve over the 381-bit prime p(z) where z = -(2^94 + 2^76 + 2^72 + 1).
    • BN462 ; a BN curve over the 462-bit prime p(z) where z = 2^114 + 2^101 - 2^14 - 1.
  • BLS12_381 ; a BLS12-381 curve



How to build on Linux and macOS

x86-64/ARM/ARM64 Linux, macOS and mingw64 are supported.

Installation Requirements

GMP is necessary (default setting).

apt install libgmp-dev # on Ubuntu

How to build with Makefile

git clone git://
cd mcl
make -j4
  • lib/libmcl.* ; core library
  • lib/libmclbn384_256.* ; library to use C-API of BLS12-381 pairing

How to test of BLS12-381 pairing

# C
make bin/bn_c384_256_test.exe && bin/bn_c384_256_test.exe

# C++
make bin/bls12_test.exe && bin/bls12_test.exe

How to build without GMP

make MCL_USE_GMP=0

Define MCL_USE_VINT if using C++ header files.

How to profile on Linux

Use perf

make MCL_USE_PROF=1 bin/bls12_test.exe
env MCL_PROF=1 bin/bls12_test.exe

Use Intel VTune profiler

Supporse VTune is installed in /opt/intel/vtune_amplifier/.

make MCL_USE_PROF=2 bin/bls12_test.exe
env MCL_PROF=2 bin/bls12_test.exe

How to build on 32-bit x86 Linux

Build GMP and for 32-bit mode and install <lib32> at yourself.

make ARCH=x86 CFLAGS_USER="-I <lib32>/include" LDFLAGS_USER="-L <lib32>/lib -Wl,-rpath,<lib32>/lib"

How to build on 64-bit Windows with Visual Studio

Clone cybozulib_ext, which provides compiled binaries of MPIR.

mkdir work
cd work
git clone git://
git clone git://
cd work
# static library
mk -s test\bls12_test.cpp && bin\bls12_test.exe
# dynamic library
mklib dll
mk -d test\bls12_test.cpp && bin\bls12_test.exe

(not maintenanced) Open mcl.sln and build or if you have msbuild.exe

msbuild /p:Configuration=Release

How to build with CMake

For Linux, macOS, etc.

mkdir build
cd build
cmake ..

For Visual Studio,

mkdir build
cd build
cmake .. -A x64
msbuild mcl.sln /p:Configuration=Release /m


cmake .. USE_GMP=OFF ; without GMP

see cmake .. -LA.

How to build for wasm(WebAssembly)

mcl supports emcc (Emscripten) and test/bn_test.cpp runs on browers such as Firefox, Chrome and Edge.

The timing of a pairing on BN254 is 2.8msec on 64-bit Firefox with Skylake 3.4GHz.



The latest benchmark(2018/11/7)

Intel Core i7-6700 3.4GHz(Skylake), Ubuntu 18.04.1 LTS

curveType binary clang-6.0.0 gcc-7.3.0
BN254 bin/bn_test.exe 882Kclk 933Kclk
BLS12-381 bin/bls12_test.exe 2290Kclk 2630Kclk

Intel Core i7-7700 3.6GHz(Kaby Lake), Ubuntu 18.04.1 LTS on Windows 10 Vmware

curveType binary clang-6.0.0 gcc-7.3.0
BN254 bin/bn_test.exe 900Kclk 954Kclk
BLS12-381 bin/bls12_test.exe 2340Kclk 2680Kclk
  • now investigating the reason why gcc is slower than clang.

Higher-bit BN curve benchmark

For JavaScript(WebAssembly), see ID based encryption demo.

paramter x64 Firefox on x64 Safari on iPhone7
BN254 0.25 2.48 4.78
BN381_1 0.95 7.91 11.74
BN462 2.16 14.73 22.77
  • x64 : 'Kaby Lake Core i7-7700(3.6GHz)'.
  • Firefox : 64-bit version 58.
  • iPhone7 : iOS 11.2.1.
  • BN254 is by test/bn_test.cpp.
  • BN381_1 and BN462 are by test/bn512_test.cpp.
  • All the timings are given in ms(milliseconds).

The other benchmark results are bench.txt.

An old benchmark of a BN curve BN254(2016/12/25).

  • x64, x86 ; Inte Core i7-6700 3.4GHz(Skylake) upto 4GHz on Ubuntu 16.04.
    • sudo cpufreq-set -g performance
  • arm ; 900MHz quad-core ARM Cortex-A7 on Raspberry Pi2, Linux 4.4.11-v7+
  • arm64 ; 1.2GHz ARM Cortex-A53 HiKey
software x64 x86 arm arm64(msec)
ate-pairing 0.21 - - -
mcl 0.31 1.6 22.6 3.9
TEPLA 1.76 3.7 37 17.9
RELIC PRIME=254 0.30 3.5 36 -
MIRACL ake12bnx 4.2 - 78 -
NEONabe - - 16 -
  • compile option for RELIC


mcl uses Xbyak JIT engine if it is available on x64 architecture, otherwise mcl uses a little slower functions generated by LLVM. The default mode enables SELinux security policy on CentOS, then JIT is disabled.

% sudo setenforce 1
% getenforce
% bin/bn_test.exe
pairing   1.496Mclk
finalExp 581.081Kclk

% sudo setenforce 0
% getenforce
% bin/bn_test.exe
pairing   1.394Mclk
finalExp 546.259Kclk

How to make asm files (optional)

The asm files generated by this way are already put in src/asm, then it is not necessary to do this.

Install LLVM.

make MCL_USE_LLVM=1 LLVM_VER=<llvm-version> UPDATE_ASM=1

For example, specify -3.8 for <llvm-version> if opt-3.8 and llc-3.8 are installed.

If you want to use Fp with 1024-bit prime on x86-64, then

make MCL_USE_LLVM=1 LLVM_VER=<llvm-version> UPDATE_ASM=1 MCL_MAX_BIT_SIZE=1024

API for Two level homomorphic encryption

Java API



modified new BSD License

This library contains some part of the followings software licensed by BSD-3-Clause.



  • mclBnGT_inv returns a - b w, a conjugate of x for x = a + b w in Fp12 = Fp6[w]
    • use mclBnGT_invGeneric if x is not in GT
  • mclBn_setETHserialization(true) (de)serialize acoording to ETH2.0 serialization of BLS12-381 when BLS12-381 is used.
  • (Break backward compatibility) libmcl_dy.a is renamed to libmcl.a
    • The option SHARE_BASENAME_SUF is removed
  • 2nd argument of mclBn_init is changed from maxUnitSize to compiledTimeVar, which must be MCLBN_COMPILED_TIME_VAR.
  • break backward compatibility of mapToGi for BLS12. A map-to-function for BN is used. If MCL_USE_OLD_MAPTO_FOR_BLS12 is defined, then the old function is used, but this will be removed in the future.


  • 2020/Jun/07 v1.22 remove old hash-to-curve functions
  • 2020/Jun/04 v1.21 mapToG1 and hashAndMapToG1 are compatible to irtf/eip-2537
  • 2020/May/13 v1.09 support draft-irtf-cfrg-hash-to-curve-07
  • 2020/Mar/26 v1.07 change DST for hash-to-curve-06
  • 2020/Mar/15 v1.06 support hash-to-curve-06
  • 2020/Jan/31 v1.05 mclBn_ethMsgToFp2 has changed to append zero byte at the end of msg
  • 2020/Jan/25 v1.04 add new hash functions
  • 2019/Dec/05 v1.03 disable to check the order in setStr
  • 2019/Sep/30 v1.00 add some functions to bn.h ;
  • 2019/Sep/22 v0.99 add mclBnG1_mulVec, etc.
  • 2019/Sep/08 v0.98 bugfix Ec::add(P, Q, R) when P == R
  • 2019/Aug/14 v0.97 add some C api functions
  • 2019/Jul/26 v0.96 improved scalar multiplication
  • 2019/Jun/03 v0.95 fix a parser of 0b10 with base = 16
  • 2019/Apr/29 v0.94 mclBn_setETHserialization supports ETH2.0 serialization of BLS12-381
  • 2019/Apr/24 v0.93 support ios
  • 2019/Mar/22 v0.92 shortcut for Ec::mul(Px, P, x) if P = 0
  • 2019/Mar/21 python binding of she256 for Linux/Mac/Windows
  • 2019/Mar/14 v0.91 modp supports mcl-wasm
  • 2019/Mar/12 v0.90 fix Vint::setArray(x) for x == this
  • 2019/Mar/07 add mclBnFr_setLittleEndianMod, mclBnFp_setLittleEndianMod
  • 2019/Feb/20 LagrangeInterpolation sets out = yVec[0] if k = 1
  • 2019/Jan/31 add mclBnFp_mapToG1, mclBnFp2_mapToG2
  • 2019/Jan/31 fix crash on x64-CPU without AVX (thanks to mortdeus)



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