on the first paper is written, "ASDDSF DFGDF ERSDKUF DFD RRVFDSDA"

on the second paper is written, "HOW ARE YOU HSHJFD SDF JGYJHNF LKJSFL"

One might say the first paper has some random letters which are generated by a computer randomly. But he might say the second paper is written by a human because "HOW ARE YOU" is not made of random letters...

But how we can describe it in mathematics? How we can prove that the second paper most probably is written by a human beign?