DNSSEC -- authenticated denial of existence : understanding zone enumeration

TL;DRAbstract

Over the years DNS has proved to be an integral part of the internet infracstructure. For our purposes, DNS is simply a large scale distributed database that maps human-readable domain names to network recognizable IP addresses. Unfortunately, authenticity of responses was not integral to the initial DNS design. This lead to the possibility of a very practical forgery of responses as displayed by Kaminsky's cache poisoning attacks. DNSSEC is primarily designed as a security extension of DNS, that guarantees authenticity of DNS responses. 
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\nTo answer invalid queries in an authenticated manner, DNSSEC initially employed the NSEC records. To its credit, NSEC allowed nameservers to precompute signatures for such negative responses offline. As a result, NSEC is highly scalable while preserving the authenticity/correctness of responses. But, while doing so, NSEC leaks domains from nameserver's zone. This is called zone enumeration. 
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\nTo counter zone enumeration, NSEC3

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