Can a public key be generated from a PGP PRIVATE KEY?

Question

I am creating the license of my java product with openpgp using the public key. The product is shipped with the private key to read the license file. Is this the right approach? Can the private key be used to generate public keys?

Thanks

Answer 1

No. Private keys should be kept private.

Use a signing mechanism. Sign with your private key to create a signature, validate that signature with your public key. The public key is then shipped with your product.

Answer 2

"Can the private key be used to generate public keys?"
As for this part of your question, I think the answer is yes. Packet Tag 5 (as per RFC 4880) contains all the data you need, including the public key. As for the proper usage, think of the public key as your debit card number and the private key as your PIN.