I will also point out that even if they are only observing ciphertext, they can still glean a lot: http://web.cs.wpi.edu/~claypool/papers/yt-crawler/final.pdf

I will also point out that even if they are only observing ciphertext, they can still glean a lot: http://web.cs.wpi.edu/~claypool/papers/yt-crawler/final.pdf http://web.cs.wpi.edu/~claypool/papers/yt-crawler/final.pdf