OpenSSL

Description
The OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, fully featured, and Open Source toolkit implementing the Transport Layer Security (TLS) protocols (including SSLv3) as well as a full-strength general purpose cryptographic library.

OpenSSL is descended from the SSLeay library developed by Eric A. Young and Tim J. Hudson. The OpenSSL toolkit is licensed under a dual-license (the OpenSSL license plus the SSLeay license), which means that you are free to get and use it for commercial and non-commercial purposes as long as you fulfill the conditions of both licenses.

From: https://github.com/openssl/openssl
Source code
Available on GitHub: https://github.com/openssl/openssl
License
OpenSSL, SSLeay
Copyright
Copyright (c) 1998-2018 The OpenSSL Project
Copyright (c) 1995-1998 Eric A. Young, Tim J. Hudson
Packages
Download OpenSSL 1.1.2-dev Windows archives here below.
Windows binary packages for OpenSSL are available for Visual Studio 2013, 2015 and 2017 ABIs, 32bit and 64bit, for MinGW 5.3.0 32 bit and MinGW 7.3.0 64 bit.
下载windows的openssl二进制文件

MSVC2013 - Visual studio 12.0

openssl-1.1.2-dev-msvc2013-x86-debug.zip
openssl-1.1.2-dev-msvc2013-x86-release.zip
openssl-1.1.2-dev-msvc2013-amd64-debug.zip
openssl-1.1.2-dev-msvc2013-amd64-release.zip

MSVC2015 - Visual studio 13.0

openssl-1.1.2-dev-msvc2015-x86-debug.zip
openssl-1.1.2-dev-msvc2015-x86-release.zip
openssl-1.1.2-dev-msvc2015-amd64-debug.zip
openssl-1.1.2-dev-msvc2015-amd64-release.zip

MSVC2017 - Visual studio 14.0

openssl-1.1.2-dev-msvc2017-x86-debug.zip
openssl-1.1.2-dev-msvc2017-x86-release.zip
openssl-1.1.2-dev-msvc2017-amd64-debug.zip
openssl-1.1.2-dev-msvc2017-amd64-release.zip

MinGW 5.3.0 - 32 bits only

openssl-1.1.2-dev-mingw530_32-debug.zip
openssl-1.1.2-dev-mingw530_32-release.zip

MinGW 7.3.0 - 64 bits only

openssl-1.1.2-dev-mingw730_64-debug.zip
openssl-1.1.2-dev-mingw730_64-release.zip