Hello, I have a question regarding encrypted bloom filter protocols. I have come to the understanding that I can use such protocols to allow a client to query a server for the presence of a string, "string". Due to the properties of the encrypted bloom filter protocol, the server is incapable of determining that the client is checking for the presence of "string". However, what interests me is if any of these protocols also support unlinkable queries, such that a client making multiple queries for the presence of "string" does not reveal to the server over a set of queries that they are checking for the presence of the same string in each query, even if the server is incapable of determining which specific string the client is checking for the presence of.
I have been looking at a few encrypted bloom filter protocols and I do not fully understand them yet, but before I spend the required time to figure one out I would like to make sure that it has this property. One potential solution I can think of is perhaps the servers can keep copies of the items which they index (which are themselves very small, around 128 bytes) and every cycle (ie: ten minutes) they hash the items with a hashing function keyed with a value computable by the client and the server (ie: the time in UTC exactly ten minutes ago when the previous cycle started), and then add these items to a new bloom filter and delete the previous bloom filter. Now if clients query the encrypted bloom filter no more than once per cycle, I believe unlinkability may be gained (if it was not there in the first place), as by definition the server is incapable of determining which object in the bloom filter than the client is checking for the presence of, and the query sent by the client must look different as it is technically querying for a completely different object than it was in previous cycles. Are there any flaw in this? Thanks! _______________________________________________ cryptography mailing list [email protected] http://lists.randombit.net/mailman/listinfo/cryptography
