This page contains short building instructions for building OpenSSL (1.1.x) from source on Windows using Microsoft Visual Studio. For more details please consult the OpenSSL documentation (INSTALL and NOTES.WIN).

The OPC UA SDK only requires the libcrypto part with a few crypto algorithms and x509 certificate handling. The libssl part is not required at all.

You can download the sourcen from https://www.openssl.org or simply clone the sources using Git.

git clone git://git.openssl.org/openssl.git

Perl - http://strawberryperl.com/
Microsoft Visual Studio - https://visualstudio.microsoft.com/
Netwide Assembler (NSAM) - https://www.nasm.us/

Perl is used to generated MS NMake Makefiles. NASM is needed to generate assembler optimized code for better performance.

The default installation directories are derived from environment variables.

Configuration	Install Prefix	OpenSSL Dir
VC-WIN32	`%ProgramFiles(x86)%\OpenSSL`	`%CommonProgramFiles(x86)%\SSL`
VC-WIN64A	`%ProgramW6432%\OpenSSL`	`%CommonProgramW6432%\SSL`

It is possible to change installation directories by using the options [--prefix=DIR] [--openssldir=OPENSSLDIR], but it is recommended to keep the defaults so that CMake's find_package(OpenSSL) command is able to find it.

Open the "Visual Studio Command Prompt" to get a shell with a working compiler toolchain. Ensure that Perl and NASM are found (if not add the paths to %PATH% variable). Then type the following commands.

> perl Configure no-idea no-mdc2 no-rc5 no-ssl2 no-ssl3 no-tls no-dtls debug-VC-WIN32
> nmake build_libs
> nmake install_dev

This will build a debug version of OpenSSL. To build the release version change debug-VC-WIN32 to VC-WIN32. To build 64bit versions you need to open the according 64 bit "Visual Studio Command Prompt", e.g. x64 Native Tools Command Prompt for VS2019 and change the configure target to VC-WIN64A.

Overview of Windows build targets:

Architecture	Debug	Release
`x86`	debug-VC-WIN32	VC-WIN32
`x86_64`	debug-VC-WIN64A	VC-WIN64A