Abstract: While most reversible data hiding in encrypted images (RDH-EI) are based on stream cipher, this paper aims to present an alternative method feasible for block-enciphered images. Before uploading data to a remote server, the content owner encrypts the original image with a block cipher algorithm using an encryption key. Then, the server embeds additional bits into the encrypted image with an embedding key to generate the marked encrypted image. On the recipient side, the additional bits can be extracted if the receiver has the embedding key. In case the receiver has only the encryption key, the marked encrypted image can be directly deciphered to a plaintext image with good quality. When both the embedding and encryption keys are available for the receiver, he can recover the original image without any errors. Compared with the existing block cipher based RDH-EI method, drawbacks of the encryption and the recovery are avoided, and good embedding payloads are achieved.

Abstract: Along with advances in information technology, cybercrime techniques also increased. There are several forms of attacks on data and information, such as hackers, crackers, Trojans, etc. The Symantec Intelligence report edition on August 2012 indicated that the attacker selected the target of attacks. The type of data is valuable and confidential. The Hackers selected the target to attack or steal interest information the first and they did not just taking random from a large amount of data. This indication worried because hackers stealing the data more planned. Therefore, today many systems reinforced with various efforts to maintain data security and overcome these attacks. Necessary methods to secure electronic messages that do not fall on those who are not authorized. One alternative is steganography. Cryptography and Steganography are the two major techniques for secret communication. Cryptography converts information from its original form (plaintext) into unreadable form (cipher text); where as in steganography is the art of hiding messages within other data without changing the data to it attaches, so data before and after the process of hiding almost look like the same. There are many different techniques are available for cryptography and steganography. The cryptography suspicion against disguised message is easily recognizable, because of the message disguised by changing the original message becomes as if illegible. While further reduce suspicion steganography disguised as a message hidden in the file. The research designed the application of steganography using Least Significant Bit (LSB) in which the previous message is encrypted using the Advanced Encryption Standard algorithm (AES) and it can restore the previously hidden data. The messages in this form application and hidden text on media digital image so as not to arouse suspicion. The result of research shown the steganography is expected to hide the secret message, so the message is not easy to know other people who are not eligible.

Abstract: Wadi and Zainal recently proposed a high definition image encryption algorithm based on a modified AES-128 block cipher in (Wirel Pers Commun 79(2):811---829, 2014). In this paper, we show that the core component of their image encryption algorithm, a modified AES-128 cipher, is insecure against impossible differential attack. The proposed impossible differential attack on the full rounds of the modified AES-128 cipher has a time complexity of around $$2^{88.74}$$288.74 encryptions with $$2^{114.06}$$2114.06 chosen plaintexts and $$2^{99}$$299 bytes of memory, in contrast to the expected security of $$2^{128}$$2128. The existence of such an attack disproves the claims made by the designers that their modified AES-128 cipher improves the security of the AES cipher and that it can subsequently be used to construct a secure image encryption scheme. The root cause of this attack, some other issues with the modified AES cipher and possible solutions are described to serve as important remarks in designing a secure image encryption scheme.

Abstract: Recently, an image encryption algorithm based on scrambling and Veginere cipher has been proposed. However, it was soon cryptanalyzed by Zhang et al. using a method composed of both chosen-plaintext attack and differential attacks. This paper briefly reviews the two attack approaches proposed by Zhang et al. and outlines their mathematical interpretations. Based on these approaches, we present an improved chosen-plaintext attack to further reduce the number of chosen-plaintexts required, which is proved to be optimal. Moreover, it is found that an elaborately designed known-plaintext attack can efficiently compromise the image cipher under study. This finding is confirmed by both mathematical analysis and numerical simulations. The cryptanalyzing techniques developed in this paper provide some insights for designing secure and efficient multimedia ciphers.

Abstract: The process of distributing information in a secured way is called Secured Communication. Secured information involves Encryption procedure at the sender side and Decryption process at the receiver side of the communication system. Many Ciphers have been developed to provide data guard. The effectiveness of the Ciphers that are being used depends mainly on their throughput and memory constraint. The proposed method encrypts two messages at a time with the help pairing function so that it reduces the size to half of original length. The key is embedded within the cipher text with the help of transposition ciphers. The proposed method decrypts the single message (which is transmitted) into two messages with the help of depairing functions.

Abstract: Maintaining the security of messages is a very important thing both within an organization and the personal especially in the age of information technology today. In order to the sent message does not fall into the one’s hands who are not interested, then encryption should be created to maintain the confidentiality of a message remains secure. Classical cryptography method using Vigenere Cipher and RSA (Riverst Shamir Adleman) is one of securing methods which will be used. In this case, the initial process is doing encryption on Vigenere cipher that produces a temporary ciphertext. The temporary ciphertext will be a plaintext on the RSA algorithm and then encrypted again to produce the actual ciphertext. Merging these two methods produces a ciphertext that is more powerful and difficult to solve.

Abstract: Playfair cipher is the first known digraph polyalphabetic method. It relies on 5x5 uppercase alphabets matrix with simple substitution processes to be used for encryption and decryption. This paper proposes an enhanced variant of Playfair cipher algorithm that incorporates an algorithm for elaborate key generation starting with a seed accompanying the ciphertext and will be referred to as a Novel Paradigm for Symmetric Cryptosystem (NPSC). The key generation, encryption and decryption processes implement modular calculations instead of the simple substitution used in the traditional Playfair cipher. It supports both alphabetic characters and numerals. This variant considerably enhances the security strength without increasing the matrix size as demonstrated by the experimentation results. Comparative studies of various critical factors with other reported versions of Playfair cipher and results were also included.

Abstract: Cryptography is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it. Cryptography includes techniques such as microdots, merging words with images, and other ways to hide information in storage or transit. However, in today's computer-centric world, cryptography is most often associated with scrambling plaintext (ordinary text, sometimes referred to as cleartext) into ciphertext (a process called encryption), then back again (known as decryption). Individuals who practice this field are known as cryptographers. To make a secure and successful transaction of message, the security of cipher text is must before transmission over communication channel. This paper propose a new encryption technique with the help of random segmentation and random re-arrangement of cipher text using two dimensional array before transmission over communication channel so that the transmitted cipher text is more complex to decrypt by any attacker.