It's much easier to tell a correct private RFC 1918 IP from four bytes of garbage. There are only 17,891,328 valid values. The odds move further in your favor

It's much easier to tell a correct private RFC 1918 IP from four bytes of garbage. There are only 17,891,328 valid values. The odds move further in your favor when you have multiple private addresses to work with -- a valid key will most likely result in addresses that are all in a single RFC 1918 block, and very possibly all in the same /24.