are these the same?

For example,
"I'm on my own" means that you are independent and responsible for yourself.
"I'm by myself" means that you are all alone.

No. "I'm on my own" also means you are by yourself, there's no-one else around.

but both of them have these meanings:
1-alone
2-unaided
so are they quite the same?

Both mean "alone" and that's the most common use of these phrases. However, in answer to the question: "Did someone help you with your English homework?" You could then respond: "No, I did it by myself." which gives you the "unaided" meaning. Thus, the context changes the meaning.

thanks for the answer,so can we use them instead of eachother?

... depending on the context, yes. You can't interchange "on my own" in the second example I gave you. ie: You can't say "I did it on my own". You will hear native speakers say that, but they will usually be children, and they will be corrected!

thank you very much.

There is actually no strict rule in terms of their meaning, so both you and me are in some way correct.
Read, for instance, this thread http://forum.wordreference.com/showthread.php?t=280005&langid=18

They agree with me.

By the way, does one really need to hyphenate

You mean "You and I are both correct". Are you American? It appears there is considerable differences then between the rules of American English and British/Australian English ...

Yes, we always use a hyphen in no-one ... otherwise it is "noone" and that's not even a word