An MD4 hash is a unique value given as a result of a mathematical expression following the MD4 algorithm which claims to ensure data integrity.
It provides a 128-bit (16 bytes, 32 hex chars) message digest from the data input (the input may be of any length) that is claimed to be unique.
- This is a bit out of date, or just uninformed. MD5 is questionable, these days (the currently existing attacks on it aren't serious for most applications, but the door is open for more), and MD4 is known to be absolutely hopeless, and collisions can be found with very little in the way of computational effort. The upshot of which is that it would be theoretically pretty easy for a rogue node to cause undetectable corruption to files on ed2k.