
Efficient storage: how we went down from 50 PB to 32 PB - r4um
https://medium.com/@andrewsumin/efficient-storage-how-we-went-down-from-50-pb-to-32-pb-99f9c61bf6b4#.ju1t29abd
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nn3
Possible security problems:

\- It may be possible to use timing to determine if a file already exists. So
it could be possible for an attacker to determine for someone if some other
mail.ru user received a file with some given contents.

\- They rely on no-one being able to construct a collision of (SHA1, CRC32,
size) I believe SHA1 collisions are at least possible. If it was possible to
construct such a collision you could change someone else's files by sending an
email earlier with the collision.

