Simple Encrypted Arithmetic Library

The Simple Encrypted Arithmetic Library is an easy-to-use homomorphic encryption library, developed by researchers in the Cryptography Research Group at Microsoft Research. SEAL is written in C++, and contains .NET wrappers for the public API. It has no external dependencies, so it is easy to compile in many different environments. SEAL uses the Microsoft Research License Agreement, and is free for research use.


12/1/2017: SEAL v2.3.0-4 available

A new update v2.3.0-4 fixing several major bugs and issues has been released. Important changes include:

  • The problem with GCC-7.2 has been fixed. SEAL also works with GCC-5 now and uses only C++11 (no C++14).
  • Homomorphic multiplication of ciphertexts of size larger than 2 gave incorrect results. This problem has been fixed now.
  • SEALNET EvaluationKeys|GaloisKeys::Save|Load now work correctly.
  • Problems with global memory pool in SEALNET have been fixed. There is no longer need to manually destroy the global memory pool on application exit.
  • In SEALNET, EncryptionParameters::SetX(…) functions have been removed and changed into setters for the corresponding properties.
  • Downloadable Linux (.tar.gz) and Windows (.zip) versions are available separately.


11/17/2017: Small updates

As some of you may have noticed, we’ve been pushing a lot of small (and big) bug fixes and other updates since the initial release of v2.3.0. We just released SEAL v2.3.0-3 which—in addition to the bug fixes—brings substantial improvements to memory locality and subsequently has a major impact on performance with larger parameters.


11/9/2017: Direct download link

SEAL v2.3.0-2 can now be downloaded directly from


11/7/2017: SEAL v2.3.0 released

A new version of SEAL is available! This is the biggest update since the first release, and contains a huge number of improvements, including:

  • Implementation of the FullRNS variant of the FV scheme by Bajard et al. (SAC 2016)
  • Redesigned and improved memory management
  • Improved support for multi-threaded applications
  • Massive number of optimizations and improvements throughout the library
  • Row and column rotations of encrypted matrices (batching)
  • Completely revised SEALExamples/main.cpp; new example demonstrating multi-threaded use of SEAL
  • Better directory structure
  • Lots of bug fixes

A new SEAL manual will be available shortly.

We highly recommend all users (especially those familiar with older versions of SEAL) to go carefully over the examples in SEALExamples/main.cpp. There are several subtle but critical differences to SEAL v2.2, which are necessary to know to achieve the best performance.


7/21/2017: SEAL has found a new home

SEAL is now available at To get access, send us an email at, include an email address associated to your Microsoft Live Account, and tell us briefly what you are planning on using SEAL for. SEAL v2.3 will be available only through the new repository.


6/4/2017: SEAL v2.2 released

SEAL v2.2 has been released. It includes the changes from the experimental branch, and many other improvements. We have big plans for major improvements to be implemented this summer, so stay tuned!


10/13/2016: Experimental Branch

A new experimental branch has been created. This branch will get much more frequent updates than the master branch, but these updates may not have been tested as thoroughly as the code in the master branch, may introduce frequent API changes, and may contain incomplete functionality. This first experimental commit contains some significant performance improvements over SEAL v2.1.


9/30/2016: SEAL v2.1 released

Again a new version of SEAL has been released. This is a fairly large update, which focuses mostly on performance, but also introduces some small API changes.

To accompany the release and to explain the changes in SEAL v2.1, we have released a new version of the documentation, available here.


SEAL v2.3.0-4 can be downloaded from

Alternatively, to get access to the git repository, send us an email at, include an email address associated to your Microsoft Live Account, and tell us briefly what you are planning on using SEAL for. We will then give you access to the git repository available through


A detailed manual for SEAL v2.2 is available here. We will release the v2.3.0 manual shortly. The manual contains a short introduction to homomorphic encryption, an explanation of changes from the previous release, and some details on how SEAL works under the hood.

The code-base contains examples written both in C++ (SEALExamples/) and in C# (SEALNETExamples/). These examples are thoroughly commented, serving as a self-contained short introduction to using the library, and demonstrating most of the basic features, and also some more advanced use-cases. In addition, the .h files both in the C++ library and in the .NET wrapper library contain detailed comments for the public API.

Going over the code examples in detail is probably the best way for a new user to get started.


Microsoft Research License Agreement for Simple Encrypted Arithmetic Library

This Microsoft Research License Agreement, including all exhibits (“Agreement”) is a legal agreement between you and Microsoft Corporation (or based on where you live, one of its affiliates). Please read them. They apply to the Microsoft Research software named above, which may include source code and any associated materials, text or speech files, associated media and “online” or electronic documentation and any updates we provide in our discretion (together, the “Software”). The terms also apply to any Microsoft (i) updates, (ii) supplements, (iii) internet-based services, and (iv) support services for this Software, unless other terms accompany those items. If so, those terms apply.
By agreeing to this Agreement and/or by using the Software, you accept these terms. If you do not accept them, do not use the Software. If you comply with these license terms, you have the rights below.
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We are always looking for talented Ph.D. student interns to work with us on the SEAL project, and related homomorphic encryption research. If you are interested in a fun and productive 12-week internship at Microsoft Research, send us an email at Internships can take place at any time of the year.

An ideal  intern candidate has a non-empty subset of the following:

  • Strong academic record; publications in top conferences/journals
  • Background in cryptography/homomorphic encryption
  • Excellent communication skills; ability to communicate difficult/technical topics to mixed audiences
  • Excellent teamwork skills; ability to work together with people of diverse backgrounds towards a common goal
  • Strong programming experience in C++; experience in writing fast code
  • Experience in a professional software engineering project, e.g. prior internship experience as a software developer
  • Experience in machine learning
  • Ability to learn new skills quickly when needed
  • Passion for solving real-life privacy problems with fresh new ideas


Current and past interns:

Nathan Dowlin (Princeton University) Rachel Player (Royal Holloway, University of London)
Gizem Cetin (Worcester Polytechnic Institute) Yuhou (Susan) Xia (Princeton University)
Peter Rindal (Oregon State University) Kyoohyung Han (Seoul National University)
Zhicong Huang (EPFL) Amir Jalali (Florida Atlantic University)


We believe strongly that (fully) homomorphic encryption is ripe for use in many real-world applications. Since the technology is still quite new, and the existing libraries are very diverse in their functionality and design, we believe that a clear and public standardization effort could help in

  • Making homomorphic encryption easier to use
  • Determining security levels for specific parameter sets
  • Explaining to the public the capabilities and possibilities of this technology
  • Making libraries more inter-operable

We hosted a workshop on July 13-14, 2017, to get the standardization discussion started. For more information, see

Contact Us

If you have any questions, suggestions, comments, or bug reports, please contact us by emailing