4 ms·
It's unlikely to happen by chance, but it can be quite vulnerable to malicious attacks.
by Uberphallus 11y ago
It's unlikely to happen by chance, but it can be quite vulnerable to malicious attacks.
- static_noise 11y agoE.g. by backing up two files which are designed to demonstrate a MD5 collision.
- avar 11y ago"Quite". Let's look at the potential attack. You're running a backup system with user-supplied data, fair enough, and one of your users has: 1) Access to an existing object, or its checksum. 2) Can write a *new* object where they intentionally produce a collision with an existing object. There's a trivial way to get around this attack in practice, which is that you just lazily write objects and don't re-write an object that exists already. This is what Git does with the objects it writes, which insulates it more from future SHA-1 collision attacks than just the security you'd get from SHA-1 itself. This means that you've changed an attack where someone can maliciously clobber an existing object to an edge case where their object just won't get backed up.
- detaro 11y agoAssuming of course that the object they want to clobber is either already backed up or processed before the malicious object. They can still attack a new object.