Security Analysis on Cloud Data Search by using one to many Order Preserving Encryption

Cloud computing economically enables the paradigm of data service out-sourcing. However, to protect data privacy, sensitive cloud data have to be encrypted before outsourced to the commercial public cloud, which makes effective data utilization service a very challenging task .For ranked search in encrypted cloud data, order preserving encryption (OPE) is an efficient tool to encrypt relevance scores of the inverted index. When using deterministic OPE, the cipher texts will reveal the distribution of relevance scores. Therefore it is called one-to-many OPE, for applications of searchable encryption, which can flatten the distribution of the plain texts. We proposed a differential attack on one-to-many OPE by exploiting the differences of the ordered cipher texts. The experimental results show that the cloud server can get a good estimate of the distribution of relevance scores by a differential attack. Thus sensitive data have to be encrypted before being outsourced to a commercial public cloud. By using recurrence score we can retrieve the file from cloud.