Simple Encrypted Arithmetic Library or SEAL is a free and open-source cross platform software library developed by Microsoft Research that implements various forms of homomorphic encryption.

Development originally came out of the Cryptonets paper, demonstrating that artificial intelligence algorithms could be run on homomorphically encrypted data.

It is open-source (under the MIT License) and written in standard C++ without external dependencies and so it can be compiled cross platform. An official .NET wrapper written in C# is available and makes it easier for .NET applications to interact with SEAL.

Microsoft SEAL supports both asymmetric and symmetric (added in version 3.4) encryption algorithms.

Microsoft SEAL comes with two different homomorphic encryption schemes with very different properties:

Data compression can be achieved by building SEAL with Zlib support. By default, data is compressed using the DEFLATE algorithm which achieves significant memory footprint savings when serializing objects such as encryption parameters, ciphertexts, plaintexts, and all available keys: Public, Secret, Relin (relinearization), and Galois. Compression can always be disabled.

There are several known ports of SEAL to other languages in active development: