「だれもしらない」　と　「だれもしりません」　のちがいはなんですか。
I saw an awesome movie the other day called "Dare mo shiranai" which in English means "Nobody knows" but from my knowledge of Japanese I was thinking if I "Dare mo shirimasen" is also correct or not. If not then can anyone please explain in details why?
ありだとうございました。

Question

「だれもしらない」　と　「だれもしりません」　のちがいはなんですか。
I saw an awesome movie the other day called "Dare mo shiranai" which in English means "Nobody knows" but from my knowledge of Japanese I was thinking if I "Dare mo shirimasen" is also correct or not. If not then can anyone please explain in details why? 
ありだとうございました。

Answer

daremoshiranai (casual non polite)

daremoshirimasen (polite)

Answer

Thank you for explaining in more details! ^_^

Answer

If use as sentence it not polite from of noboby know It not complete sentence but use as one expresion mean  privite secet or privacy For exmaple  それは、だれもしらない　（It's my privite）（murmuring or whisper usually).
others ware It is noboby know For example それははだれもしりません( it nobody know this ) (say to public)　
as acknowgage