The process is blind, but it's fairly easy to know who the author is just due to the topic at hand. At least for specific subfields.
The hard part in this is remaining silent and pretending you don’t know anything about this, when you meet your peers at conferences.
Even if all these clues could be effectively removed, the nature of the research work, tools used, writing style, all unambiguously indicate authorship to someone in the field. I think for this reason double-blind review is not popular.
Which is not to say that it would be great if it were possible...
See the "anonymity" section.