[athrowaway3z]

'breaking' a hash can mean many different things. Among many others, two types of attacks are:

- a specific prefix/suffix data can be created to force a collision.

- A message of exactly N bytes can quickly create a collision.

Both attacks would be reported as a hash being broken. But its assumed to be unlikely that a well designed hash would have a flaw that breaks the hash in both ways. Keyword being assumed. But with good reason.

AFAIK sha has only been broken by a variable length suffix attack.

With sha2(sha2()) it would have to be broken both ways.