5, authors have proposed practical symmetric searchable encryption method. In
this scheme the file is encrypted word by word. To search for a keyword, user
sends the encrypted keyword and the key to the cloud. This key shall be used to
operate on the encrypted user data and then decrypted keyword shall be used to
search in decrypted data. The drawback of this scheme is that the word
frequency will be revealed. In 6, the first public key encryption with
keyword search (PEKS) was proposed that lead to asymmetric searchable
encryption method. The scheme suffers from
inference attack (illegitimate knowledge of data in cloud) on trapdoor searchable
encryption method. In 7 8, different techniques
that work on encrypted data were discussed, along with comparative study of
different searchable and homomorphic encryption schemes.
These existing solutions are not sufficient to protect data in cloud from unauthorized
users because of low degree of transparency. Since the cloud user and the cloud
provider are in the different trusted domain, the outsourced data may be
exposed to the vulnerabilities 10 11 12 13 14 15. To preserve the
data privacy we need to design a searchable algorithm that works on encrypted
data 16. The search techniques may use single keyword or multiple keywords
17. In larger database the search may result in many documents to be matched
with keywords. This causes difficulty for a cloud user to go through all
documents. Search based on ranking is another solution, wherein the documents
are ranked based on their relevancy to the keywords 18.
searchable encryption related studies, computation time and computation
overhead are the two most frequently used parameters for analyzing the
performance of their schemes. Computation time (also called “running
time”) is the length of time required to perform a computational process
for example searching a keyword, generating trapdoor etc. Computation overhead
is related to CPU utilization in terms of resource allocation measured in time. Thus, an effective high performance multi-keyword ranked
search over the encrypted cloud data is required. In
9 19, authors have proposed & analyzed performance of two efficient searchable
encryption schemes: CRSA/B+ tree and ECC/B+ tree.
this paper, the performance of ECC/B+ tree is analyzed under multi-user
environment and compared the same with single user.