Query-Biased Preview over Outsourced and Encrypted Data

Algorithm 2

Encrypting a document: 𝙴𝙳_𝐾(𝑑).

Input: a document 𝑑, the encryption key 𝐾

Output: the encrypted document 𝐷=𝐷₁,…,𝐷_𝑛, a keyword-frequency

set collection 𝑒=𝑒₁,…,𝑒_𝑛

Method:

 (1) padding 𝑑 according to snippet length |𝑠| as discussed

 (2) treat 𝑑 as 𝑛=|𝑑|/|𝑠| pieces 𝑠₁,…,𝑠_𝑛

 (3) for  (𝑖=1;𝑖≤𝑛;𝑖++)  do

 (4) create a keyword-frequency set 𝑒_𝑖 for 𝑠_𝑖

 (5) scan 𝑠_𝑖 for distinct valid keywords. For each keyword, count the

   keyword frequency, and add the vector (keyword, frequency) to

   𝑒_𝑖 as set element

 (6) encrypting the snippet as 𝐷_𝑖←𝙴𝚂.𝙴𝚗𝚌_𝐾𝑠_𝑖

 (7) end for