Testing Image Encryption by Output Feedback (OFB)

When it is necessary to securely transmit data in open networks, the encryption must be performed. Most of the cryptographic algorithms were mainly developed for text data. Unfortunately, algorithms those are good for textual data might not suitable for image. The OFB mode of encryption implemented to test five images of different resources, by using three combinations (schemes): a combination of an 8-bit input block with an 8-bit feedback block, a combination of an 8-bit input block with a 16-bit, or a combination of a 16-bit input block with a 16-bit feedback block. Results showed that higher degree of encryption achieved when the input block and the feedback block are of the same size. The OFB mode achieved a mid range level of encryption with a mean entropy value of 7.93.