An application on combining of cryptography and steganography for improving security

To hide hidden data in digital images, a variety of techniques are available, some of which are more complex than others. Public key cryptography is very useful for applications, and the technique used depends on the requirements for encryption and encryption data. Hiding is a kind of hiding method in which the host image is exactly retrievable. Presence lossless makes this technique suitable for medical and military applications. The image pixels are replaced with additional data into new values to embed several data pixels by S-block at multiple layers. From the original image, the embedded data can be extracted and the original image can be recovered from the decrypted image directly. Embedded data can be extracted directly from the encrypted domain. The decryption of the original plaintext image doesn't affect the data embedding operation. With the combined technique, before decryption, a receiver may extract a part of embedded data, and recover the original plaintext image after decryption. A slight distortion is introduced due to the compatibility between the lossless and reversible schemes. The data embedding operations can be performed in the two manners simultaneously performed in an encrypted image and decrypted image. In this thesis, the design of Caesar cipher and Vigenere cipher is presented. Block 4 provides good encryption properties and software productivity. The proposed technique for the design of S-box chain chaos provides a very high level of safety. The result of the implementation shows that the proposed method is suitable for lightweight cryptography due to the use of low resources using the C # .Net implementation tool. This study aims to improve the data hiding in images by using a different expansion method. It also aims to combine data hiding schemes with probabilistic and S-block properties for images encrypted by public key cryptosystems through using both cryptography and steganography. Another objective of the thesis is to present a study of reversible S-block-based data hiding techniques proposed so far in order to define the purpose of S-block-based data hiding, reflecting recent progress, and by drawing attention to some research issues for the future. This project proposes the hypothesises that a strong security application can be implemented through using both cryptography and steganography techniques. The application uses the formation of both skills to build an effective crossed platform which can be used for high protection and security purposes for files and data. This study is important in the security process; it can also be a better step towards the software threats because software threats are equally progressed as long as there is development of the computing and electronic systems. The data is taken randomly from various different software forms such as texts, PDFs, DOCs, images, etc. The procedure is done by using an application, which is built with both cryptography and steganography. The file first is encrypted and then in the second step it goes through the steganography process or vice versa. What is worth mentioning is, a file undergoes one of the above skills for protection, but the security is doubled through using both skills in one application. Hence the breaking process would be extremely difficult. This study concludes that in the lossless scheme, the embedded data can be directly extracted in the encrypted domain, and the data embedding operation is not affecting the decryption of the original plaintext image. In the reversible scheme, the additional data can be extracted from the plaintext domain, and, although a slight distortion is introduced in the decrypted image, the original plaintext image can be recovered without any error. Due to the compatibility of the two schemes, the data embedding operations of the lossless and the reversible schemes can be simultaneously performed in an encrypted image. Thus, the receiver may extract a part of embedded data in the encrypted domain, extract another part of embedded data in the plaintext domain and recover the original plaintext image in the plaintext domain. Keywords: Image Encryption, Lossless Data Hiding, Data Hiding, Public Key Encryption, Caesar Cipher.