Everything I learned about authentication, I learned at this company by digging the code base and understanding our customer's problems. I don't think this is the same like "I worked a lot with XY web framework so I start a startup with XY." I actually learned the domain of authentication only on company time.
> If its not ethical why not build it in your current company?
That's a good question I'm not allowed to answer here :D
This is what "work" accomplishes. You go to work, exchange your time for services done for the company. In exchange, the company gives you money, and yes - extreme amounts of domain knowledge, to the extent that you might be the only person on the planet who knows X topic. Then you take it to the next workplace, to spread it and to innovate. If your current company doesn't like it, they can 1) increase the pay - like pay you so much money that you're willing to stay. or 2) sue you and crush you so that even if you go elsewhere lawyers will be on you everywhere you go.
This is how every single person alive on the planet does it.
Without knowledge transfer and this type of behaviour, we would never progress beyond the industrial age.
True, but that same type of argument can be made for any of us. It's important not to take that argument too far, though. Remember that your company benefits from you learning & growing as well.
To be honest, I think the same way as you do. I feel really bad being a dick to an employer because I feel like I owe them something (although many HN'ers would argue we owe our employers nothing).
For me, it's helpful to make my guilt concrete - do I feel like I owe something to the company, or to specific people who mentored me? Usually it's the latter. And usually - hopefully - if they're good people, they'd be understanding if I made a decision that's best for me.
The advice I'd give to you is do what's best for you, which in this case seems like quitting and working on what you care about. But also show appreciation for the people that helped you along the way and don't burn bridges. A heartfelt thank you note/email (specific & different for each person) goes a long, long way. People remember these things and will think of you in the future.
And if they don't care or remember? Then you made the right choice to leave.
Under this logic your'e stuck with your current employer forever. Resumes and interviews are all about what you learned at your previous jobs, so if you don't want to make use of that anywhere else, then you might as well shred your resume and forget about ever getting hired ¯\_(ツ)_/¯.
I bet your company goes around hiring experienced people and in fact I would bet that codebase was written by someone who had worked in authentication before, probably somewhere else. So unless it's not illegal (like company secrets) nothing to worry about.