PEAS stands for Private, Efficient and Accurate (web) Search.

It is composed of the following protocols:

• an unlinkability protocol (peas_unlink): aims at hiding users identity,
• an indistinguishability protocol (peas_indist): aims at hiding users intents by obfuscating their queries,

The request and response formats handled in these protocols are described here.

The PEAS protocol considers specific formats to exchange data. These formats are described here.

Installation

git clone https://github.com/EEXCESS/peas.git folderOfYourChoice
cd folderOfYourChoice/
git checkout master
bower install

Indistinguishability Protocol

The component offers two techniques to do query obfuscation and result set filtering.

Obfuscation

The method is defined as follows:

/**
 * Generates an obfuscated query composed of (k+1) queries: 
 * 1 real query (the one given as input) and k fake queries. 
 * @method obfuscateQuery
 * @param {JSONObject} query A query of format QF1.
 * @param {Integer} k The desired number of fake queries. 
 * @return {JSONObject} A query of format QF2. 
 */
obfuscateQuery(query, k){ ... }

This example shows how to use it:

require(["peas_indist"], function(peas_indist){
	// Query of format QF1:
	var originalQuery = JSON.parse('{"numResults":3,"contextKeywords":[{"text":"graz","weight":0.1},{"text":"vienna", "weight":0.1}]}'); // A query in the format QF1
	var nbFakeQueries = 3; 
	// Query of format QF2:
	var obfuscatedQuery = peas_indist.obfuscateQuery(originalQuery, nbFakeQueries);  // Returns a query composed of (nbFakeQueries+1) sub-queries
	// The obfuscated query can be sent to the privacy proxy to be processed
	// The orginal query can also be send to the privacy proxy
});

Filtering

The method is defined as follows:

/**
 * Filters a result set and returns the results corresponding to the original query given as input. 
 * @method filterResults
 * @param {JSONObject} results A result set of format RF2. 
 * @param {JSONObject} query A query of format QF1. 
 * @return {JSONObject} A result set of format RF1. 
 */
filterResults(results, query){ ... }

This example shows how to use it:

require(["peas_indist"], function(peas_indist){
	// Query of format QF1:
	var originalQuery = JSON.parse('{"numResults":1,"contextKeywords":[{"text":"graz","weight":0.1},{"text":"vienna", "weight":0.1}]}'); 
	// Query of format QF2: 
	var obfuscatedQuery = JSON.parse('{"numResults":1,"contextKeywords":[[{"text":"graz","weight":0.1},{"text":"vienna","weight":0.1}],[{"text":"music","weight":0.1},{"text":"bass","weight":0.1}],[{"text":"money","weight":0.1},{"text":"euro","weight":0.1}]]}'); 
	// Results of format RF2:
	var results = JSON.parse('{"result":[[{"documentBadge":{"provider":"Europeana","id":"/2022365/Bristol_20Museums_2C_20Galleries_20_26_20Archives_emu_ecatalogue_britisharchaeology_167417","uri":"http://europeana.eu/resolve/record/2022365/Bristol_20Museums_2C_20Galleries_20_26_20Archives_emu_ecatalogue_britisharchaeology_167417"},"title": "Rebec (musical instrument bridge)."}],[{"documentBadge":{"provider":"Europeana","id":"/92070/BibliographicResource_1000126223366","uri":"http://europeana.eu/resolve/record/92070/BibliographicResource_1000126223366"},"title": "Kirche der Barmh. Schwestern zur unbefleckten Empfngniss, Graz"}],[{"documentBadge":{"provider":"Europeana","id":"/2022374/Manchester_20Museum_mm_emu_ecatalogue_humanities_98449","uri": "http://europeana.eu/resolve/record/2022374/Manchester_20Museum_mm_emu_ecatalogue_humanities_98449"},"title":"1 euro"}]],"totalResults":3,"provider":"federated"}');
	// Results of format RF1
	var filteredResults = peas_indist.filterResults(results, originalQuery);
});

Initialization

The method is defined as follows:

/**
 * Allows to change the default URL of the server hosting the PEAS external services. 
 * The default value is: https://eexcess-dev.joanneum.at/eexcess-privacy-proxy-issuer-1.0-SNAPSHOT/issuer/
 * @method initUrl
 * @param {String} url URL of the server. 
 */
init(url){ ... }

This example shows how to use them:

require(["peas_indist"], function(peas_indist){
	peas_indist.init("http://localhost:8080/eexcess-privacy-proxy-issuer-1.0-SNAPSHOT/issuer/");
});

JSON formats

Co-occurrence graph

The protocol considers a co-occurrence graph of terms. In such a graph, vertices are terms and edges are frequencies. The JSON format used to represent co-occurrence graphs is as follow:

[{
	"term": "aaa", 
	"frequencies": [
		{"term": "bbb", "frequency": 2}, 
		{"term": "ccc", "frequency": 5}
	]
},{
	"term": "bbb", 
	"frequencies": [
		{"term": "ccc", "frequency": 8}
	]
}]

This example represents the case where aaa and bbb appeared together in 2 queries, aaa and ccc in 5 queries, and bbb and ccc in 8 queries. As the co-occurrence relationship is symmetric, the graph is somehow compacted (i.e., it is not necessary to specify that bbb and aaa appeared together in 2 queries). The lexicographical order is used to determine if a pair (x, y) should be stored.

Cliques

A clique is a sub-graph of a co-occurrence graph. Therefore, the JSON format to represent a clique is similar to the one used for a co-occurrence graph. A set of cliques is simply represented as an array of graph:

[
	[{
		"term": "aaa", 
		"frequencies": [ ... ]
	},{
		"term": "bbb", 
		"frequencies": [ ... ]
	}]
]