A fast and portable C++20 library for Oblivious Transfer extension (OTe). The primary design goal of this library to obtain high performance while being easy to use. Checkout version 1.6 for the previous version.

Semi-honest OT extension:

• 1-out-of-2 Silent OT [BCGIKRS19],[RRT23].
• 1-out-of-2 OT [IKNP03].
• 1-out-of-2 Correlated-OT [IKNP03],[BLNNOOSS15].
• 1-out-of-2 OT [Roy22].
• 1-out-of-N OT [KKRT16].

Malicious OT extension:

• 1-out-of-2 Silent OT [BCGIKRS19],[RRT23].
• 1-out-of-2 OT [KOS15].
• 1-out-of-2 Correlated-OT [KOS15].
• 1-out-of-2 OT [Roy22].
• 1-out-of-2 base OT, several protocols.

Vole:

• Generic subfield noisy VOLE (semi-honest) [BCGIKRS19]
• Generic subfield silent VOLE (malicious/semi-honest) [BCGIKRS19],[RRT23].

This library provides several different classes of OT protocols. First is the base OT protocol of [CO15, MR19, MRR21]. These protocol bootstraps all the other OT extension protocols. Within the OT extension protocols, we have 1-out-of-2, 1-out-of-N, and VOLE both in the semi-honest and malicious settings. See The frontend or libOTe_Tests folder for examples.

All implementations are highly optimized using fast SSE instructions and vectorization to obtain optimal performance both in the single and multi-threaded setting.

Networking can be performed using both the sockets provided by the library and external socket classes. The simplest integration can be achieved via the message passing interface where the user is given the protocol messages that need to be sent/received. Users can also integrate their own socket type for maximum performance. See the coproto tutorial for examples.

The library is cross platform and has been tested on Windows, Mac and Linux. There is one mandatory dependency on coproto (networking), and three optional dependencies on libsodium, Relic, or SimplestOT (Unix only) for Base OTs. Boost Asio tcp networking and OpenSSL support can optionally be enabled. CMake 3.15+ is required and the build script assumes python 3.

The library can be built with libsodium, all OT protocols enabled and boost asio TCP networking as

git clone https://github.com/osu-crypto/libOTe.git cd libOTe python build.py --all --boost --sodium 

The main executable with examples is frontend and is located in the build directory, eg out/build/linux/frontend/frontend, out/build/x64-Release/frontend/frontend.exe depending on the OS.

LibOTe can be built with various only the selected protocols enabled. -D ENABLE_ALL_OT=ON will enable all available protocols depending on platform/dependencies. The ON/OFF options include

Malicious base OT:

• ENABLE_SIMPLESTOT the SimplestOT [CO15] protocol (relic or sodium).
• ENABLE_SIMPLESTOT_ASM the SimplestOT base OT protocol [CO15] protocol (linux assembly).
• ENABLE_MRR the McQuoid Rosulek Roy [MRR20] protocol (relic or sodium).
• ENABLE_MRR_TWIST the McQuoid Rosulek Roy [MRR21] protocol (sodium fork).
• ENABLE_MR the Masny Rindal [MR19] protocol (relic or sodium).
• ENABLE_MR_KYBER the Masny Rindal [MR19] protocol (Kyber fork).
• ENABLE_NP the Naor Pinkas [NP01] base OT (relic or sodium).

1-out-of-2 OT Extension:

• ENABLE_IKNP the Ishai et al [IKNP03] semi-honest protocol.
• ENABLE_KOS the Keller et al [KOS15] malicious protocol.
• ENABLE_DELTA_KOS the Burra et al [BLNNOOSS15],[KOS15] malicious Delta-OT protocol.
• ENABLE_SOFTSPOKEN_OT the Roy Roy22 semi-honest/malicious protocol.
• ENABLE_SILENTOT the [BCGIKRS19],[RRT23] semi-honest/malicious protocol.

Vole:

• ENABLE_SILENT_VOLE the [BCGIKRS19],[RRT23] semi-honest/malicious protocol.

Addition options can be set for cryptoTools. See the cmake output.

Dependencies can be managed by cmake/build.py or installed via an external tool. If an external tool is used install to system location or set -D CMAKE_PREFIX_PATH=path/to/install. By default build.py calls cmake with the command line argument

-D FETCH_AUTO=true 

. This tells cmake to first look for dependencies on the system and if not found then it will be downloaded and built automatically. If set to false then the build will fail if not found. Each dependency can downloaded and build for you by explicitly setting it's FETCH_*** variable to true. See blow. The python build.py script by default sets FETCH_AUTO=true and can be set to false by calling it with --noauto.

Enabling/Disabling Relic (for base OTs): The library can be built with Relic as

python build.py --relic 

Relic can be disabled by removing --relic from the setup and setting -D ENABLE_RELIC=false. This will always download and build relic. To only enable but not download relic, use python build.py -D ENABLE_RELIC=true.

Enabling/Disabling libsodium (for base OTs): The library can be built with libsodium as

python build.py --sodium 

libsodium can be disabled by removing --sodium from the setup and setting -D ENABLE_SODIUM=false. This will always download and build sodium. To only enable but not download relic, use python build.py -D ENABLE_SODIUM=true.

The McQuoid Rosulek Roy 2021 Base OTs uses a twisted curve which additionally require the noclamp option for Montgomery curves and is currently only in a fork of libsodium. If you prefer the stable libsodium, then install it and add -D SODIUM_MONTGOMERY=false as a cmake argument to libOTe.

Enabling/Disabling boost asio (for TCP networking): The library can be built with boost as

python build.py --boost 

boost can be disabled by removing --boost from the setup and setting -D ENABLE_BOOST=false. This will always download and build boost. To only enable but not download relic, use python build.py -D ENABLE_BOOST=true.

Enabling/Disabling OpenSSL (for TLS networking): The library can be built with boost as

python build.py --openssl 

OpenSSL can be disabled by removing --openssl from the setup and setting -D ENABLE_OPENSSL=false. OpenSSL is never downloaded for you and is always found using your system installs.

libOTe can be installed and linked the same way as other cmake projects. To install the library and all downloaded dependencies, run the following

python build.py --install 

Sudo is not used. If installation requires sudo access, then install as root. See python build.py --help for full details.

libOTe can be linked via cmake as

find_package(libOTe REQUIRED) target_link_libraries(myProject oc::libOTe) 

Other exposed targets are oc::cryptoTools, oc::tests_cryptoTools, oc::libOTe_Tests. In addition, cmake variables libOTe_LIB, libOTe_INC, ENABLE_XXX will be defined, where XXX is one of the libOTe options.

To ensure that cmake can find libOTe, you can either install libOTe or build it locally and set -D CMAKE_PREFIX_PATH=path/to/libOTe or provide its location as a cmake HINTS, i.e. find_package(libOTe HINTS path/to/libOTe).

libOTe can be found with the following components:

find_package(libOTe REQUIRED COMPONENTS std_20 Debug Release RelWithDebInfo boost relic sodium bitpolymul openssl circuits sse avx asan pic no_sse no_avx no_asan no_pic simplestot simplestot_asm mrr mrr_twist mr mr_kyber kos iknp silentot softspoken_ot delta_kos silent_vole oos kkrt ) 

Contact Peter Rindal peterrindal@gmail.com for any assistance on building or running the library.

Spread the word!

@misc{libOTe, author = {Peter Rindal, Lance Roy}, title = {{libOTe: an efficient, portable, and easy to use Oblivious Transfer Library}}, howpublished = {\url{https://github.com/osu-crypto/libOTe}}, } 

[NP01] - Moni Naor, Benny Pinkas, Efficient Oblivious Transfer Protocols.

[IKNP03] - Yuval Ishai and Joe Kilian and Kobbi Nissim and Erez Petrank, Extending Oblivious Transfers Efficiently.

[KOS15] - Marcel Keller and Emmanuela Orsini and Peter Scholl, Actively Secure OT Extension with Optimal Overhead. eprint/2015/546

[OOS16] - Michele Orrù and Emmanuela Orsini and Peter Scholl, Actively Secure 1-out-of-N OT Extension with Application to Private Set Intersection. eprint/2016/933

[KKRT16] - Vladimir Kolesnikov and Ranjit Kumaresan and Mike Rosulek and Ni Trieu, Efficient Batched Oblivious PRF with Applications to Private Set Intersection. eprint/2016/799

[RR16] - Peter Rindal and Mike Rosulek, Improved Private Set Intersection against Malicious Adversaries. eprint/2016/746

[BLNNOOSS15] - Sai Sheshank Burra and Enrique Larraia and Jesper Buus Nielsen and Peter Sebastian Nordholt and Claudio Orlandi and Emmanuela Orsini and Peter Scholl and Nigel P. Smart, High Performance Multi-Party Computation for Binary Circuits Based on Oblivious Transfer. eprint/2015/472

[ALSZ15] - Gilad Asharov and Yehuda Lindell and Thomas Schneider and Michael Zohner, More Efficient Oblivious Transfer Extensions with Security for Malicious Adversaries. eprint/2015/061

[CRR21] - Geoffroy Couteau ,Srinivasan Raghuraman and Peter Rindal, Silver: Silent VOLE and Oblivious Transfer from Hardness of Decoding Structured LDPC Codes.

[Roy22] - Lawrence Roy, SoftSpokenOT: Communication--Computation Tradeoffs in OT Extension. eprint/2022/192

[RRT23] - Srinivasan Raghuraman, Peter Rindal and Titouan Tanguy, Expand-Convolute Codes for Pseudorandom Correlation Generators from LPN. eeprint/2023/882