The invention belongs to the technical field of image deduplication and discloses a
ciphertext image deduplication method used in the cloud environment and a
cloud server. An image in a
database is partitioned, characteristic values of image blocks are calculated, and the image blocks and the characteristic values are encrypted with any one rapid symmetrical
encryption algorithm; the encrypted image blocks, a sequence matrix of the image blocks and the encrypted characteristic values are uploaded to the
cloud server, and
ciphertext image deduplication operation is executed by the
server; if other authorized users upload the image again, the encrypted image blocks and the encrypted characteristic values are required to be sent to the
cloud server, the cloud
server performs retrieval operation in an encrypted image
library, and storage of the image blocks or deduplication is decided according to the fact that whether the same characteristic values of the image blocks or the characteristic values of the image blocks in a set threshold value range exist. On the basis of conventional image deduplication, safe deduplication of
ciphertext images is realized, deduplication of different images is realized, the expected safety purpose is achieved, and besides, the
storage efficiency is improved under the condition that the accuracy is guaranteed.