A Hash is a dictionary-like collection of unique keys and their values. Also called associative arrays, they are similar to Arrays, but where an Array uses integers as its index, a Hash allows you to use any object type. You retrieve or create a new entry in a Hash by referring to its key.
There is a built in easy way to read files in binary within VBA, however it has a restriction of 2GB (2,147,483,647 bytes - max of Long data type). As technology evolves, this 2GB limit is easily breached. e.g. an ISO image of Operating System install DVD disc. Microsoft does provide a way to overcome this via low level Windows API and here is a backup of it.
Also demonstrate (Read part) for calculating File Hashes without external program like
fciv.exe from Microsoft.