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Example of verifying a license key's authenticity using RSA-SHA256 with PKCS1 v1.5 padding
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Example C++ Cryptographic Verification

This is an example of cryptographically verifying a license key's authenticity using your Keygen account's public key. You can find your public key within your account's settings page.

This example implements the RSA_2048_PKCS1_SIGN scheme. Cryptographically verifying schemed licenses can be used to implement offline licensing, as well as to add additional security measures to your licensing model. All that is needed to cryptographically verify a license is your account's public key.

Running the example

First up, add an environment variable containing your public key:

# Your Keygen account's public key (make sure it is *exact* - newlines and all)
export KEYGEN_PUBLIC_KEY=$(printf %b \
  '-----BEGIN PUBLIC KEY-----\n' \
  'zdL8BgMFM7p7+FGEGuH1I0KBaMcB/RZZSUu4yTBMu0pJw2EWzr3CrOOiXQI3+6bA\n' \
  'efK41Ml6OwZB3tchqGmpuAsCEwEAaQ==\n' \
  '-----END PUBLIC KEY-----')

You can either run each line above within your terminal session before starting the app, or you can add the above contents to your ~/.bashrc file and then run source ~/.bashrc after saving the file.

Next, on macOS, install OpenSSL v1.0.2p using homebrew.

brew install openssl@1.0.2

Next, on macOS, compile the source using g++:

g++ main.cpp -o bin.out \
  -std=c++17 \
  -lssl \
  -lcrypto \
  -I /usr/local/opt/openssl/include \
  -L /usr/local/opt/openssl/lib

Then run the script, passing in the key as the first argument:

./bin.out "{KEYGEN_LICENSE_KEY}"

The license key's authenticity will be verified using RSA-SHA256 with PKCS1 v1.5 padding. Be sure to copy your public key and license key correctly - your keys will fail validation if these are copied or included incorrectly. You can find your public key in your account's settings.

Running on other platforms

We are only including instructions on how to compile and run this example on macOS. If you'd like to create a PR with instructions for another platform, such as Windows or Linux, please feel free to open a PR.


Reach out at if you have any questions or concerns!

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