Joshua, 29, will defend his IBF, WBA and WBO titles against unbeaten American Miller, BBC Sport reported.
Miller believes Joshua's claims of "being a thug" are not true because of his home county’s upbringing.
"He is from an area not known for being tough," Miller told BBC.
"He is just talking himself up but people love you being real."
Brooklyn-born Miller, 30, grew up in a "rough broken home" and said he took up combats sports to defend himself after being attacked in the street.
Joshua, meanwhile, was raised in Hertfordshire but, until the age of 14, lived on Watford's Meriden estate – one of the town's most deprived areas.
Miller has previously suggested Joshua had benefitted from a privileged route to success, to which his opponent responded by saying, "I got banned from the area I was growing up in because I was getting into too much trouble.
"The state of my hands – this isn't from boxing, this is from street fighting. I've changed my whole lifestyle around."
Both fighters are unbeaten and Miller – who is nicknamed "Big Baby" – said he will show his "grit" before claiming glory on home territory.
Miller – likely to be Joshua's heaviest professional opponent having weighed 22st 7lbs in his last contest – said, "I'm more intelligent than AJ, but sometimes I come across as arrogant because I'm a warrior.
"There is no such thing as being humble at war.
"The mental focus is about picturing the aftermath, but before I get to the glory, I have to show the grit."