1. Preparation

Before you can compile OpenSSL, some tools need to be installed.

What do I need?

Tool	For what?	Required?
Visual Studio 2022	C/C++ Compiler	Yes
Strawberry Perl	Configuration scripts	Yes
NASM	Assembly optimizations	Recommended
Git	Download source code	Yes
Windows SDK	Header files	Yes (usually included with VS)

Quick Installation

For the impatient: These three commands install everything you need:

# Visual Studio 2022 Community (free)
winget install Microsoft.VisualStudio.2022.Community
 
# Perl for build scripts
winget install StrawberryPerl.StrawberryPerl
 
# NASM for faster cryptography
winget install NASM.NASM

After installation: Restart computer so all paths are set!

Detailed Guides

Install Windows Tools - Step by step
Set up WSL2 - For Linux builds on Windows
Emscripten SDK - For WASM/Blazor builds

Verification

After installation you can check if everything works:

# 1. Load Visual Studio environment
& "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat"
 
# 2. Check C compiler
cl
# Expected output: Microsoft (R) C/C++ Optimizing Compiler Version 19.xx
 
# 3. Check Perl
perl -v
# Expected output: This is perl 5, version xx
 
# 4. Check NASM (optional)
nasm -v
# Expected output: NASM version 2.xx

Frequently Asked Questions

Q: Do I need Visual Studio Professional/Enterprise?

No! Visual Studio Community is free and sufficient.

Q: Can I use a different C compiler?

Theoretically yes (MinGW, Clang), but the Microsoft compiler is best tested for Windows.

Q: What is NASM and do I really need it?

NASM is an assembler. OpenSSL has hand-optimized assembly routines for AES, SHA, etc. Without NASM, slower C implementations are used. For production builds: Install NASM!

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Wolfgang van der Stille @ EMSR DATA d.o.o. - Post-Quantum Cryptography Professional

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