The Hashed URI
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There are situations where it is desirable to determine whether two URIs are identical without revealing the value of one or the other if they are not. For example, the publisher of filtering software may want to provide a set of URLs to be filtered without identifying the actual resources in question. This problem has traditionally been done using cryptographically secure hashes. The two items are both hashed and the resulting values then compared. If they are equal it can be assumed that the two original items were equal as well; if not, the hash does not reveal anything about the original item. This technique is eminently suitable for this situation. This document describes a 'hashed' URI naming scheme for representing the hashed form of a URI [RFC2396] as another URI.