#Dll license key generator .dll

The signatures should be part of the license key. The product should validate the license keys with the corresponding public key.

This way, even if someone has full access to your product's logic, they cannot generate license keys because they don't have the private key.

#Dll license key generator .dll

A license key would look like this: BASE32(CONCAT(DATA, PRIVATE_KEY_ENCRYPTED(HASH(DATA)))) #DLL CARE 1.0 LICENSE KEY FULL# The biggest challenge here is that the classical public key algorithms have large signature sizes. You don't want your license keys to have hundreds of characters. One of the most powerful approaches is to use elliptic curve cryptography (with careful implementations to avoid the existing patents). You can further reduce the signature sizes using algorithms like the Schnorr digital signature algorithm (patent expired in 2008 - good :) ) ECC keys are like 6 times shorter than RSA keys, for the same strength. This is achievable by product activation (Windows is a good example).

Basically, for a customer with a valid license key, you need to generate some 'activation data' which is a signed message embedding the computer's hardware id as the signed data.

This is usually done over the internet, but only ONCE: the product sends the license key and the computer hardware id to an activation server, and the activation server sends back the signed message (which can also be made short and easy to dictate over the phone).