> Practically this means exploitation opportunities are rather limited, but a forced collision being possible at all seems non-ideal for an adversarial use case

> Practically this means exploitation opportunities are rather limited, but a forced collision being possible at all seems non-ideal for an adversarial use case. There's also the risk that future cryptanalysis will further weaken MD5. Seems clear to me WeChat just should have used something like sha256. With a billion people using phones, "good enough" is probably good enough. Given the scale and scope of the Chinese security apparatus, anyone capable of using a GPU to hash out collisions is probably already known to the state. And the handful of collisions are probably not important enough to worry about -- a stealthy Winnie The Poo image isn't a big deal.