In this paper, Advanced Encryption Standard was modified to address the low diffusion rate at the early rounds by adding additional operations in both the cipher round and the key schedule. The cipher round modifications for rounds 1 to 9 of the encryption cycle were the addition of XOR operation between the SubBytes and the ShiftRow processes and the inclusion of modulo addition between the ShiftRow and MixColumn operations. In the final round of the encryption cycle, modulo addition is inserted between the SubBytes and the ShiftRow. In the decryption cycle of the cipher round, all functions were replaced by their inverses, e.g. SubBytes to InverseSubBytes, Modulo Addition to Modulo Subtraction and so on. Furthermore, the modification in the key schedule algorithm were byte substitution and round constant addition appended to the key schedule algorithm before the key expansion. The byte substitution was utilized by transforming the bytes of the 128-bit master cipher key using the AES S-box and then the result was divided into four 32-bit words. Each word was then XORed with a variable round constant dependent on a specific byte value of the word. The metrics used for evaluation were avalanche effect and frequency test to measure the diffusion and confusion characteristics respectively. Avalanche effect was measured by changing one bit of the input plaintext and determining the percentage of bits that have changed states in the cipher text. While the frequency test determines the randomness of the string by assessing the distribution of ones and zeros. The results of the avalanche effect and the frequency test of the modified AES cipher round and key schedule was compared to the standard AES. The results of the avalanche effect evaluation show that there was an average increase in diffusion of 61.98% in round 1, 14.79% in round 2 and 13.87% in round 3. Consequently, the results of the frequency test demonstrated an improvement in the randomness of the ciphertext since the average difference between the number of ones to zeros is reduced from 11.6 to 6.4 bits along with better-computed p-values. The results clearly show that the modified AES has improved diffusion and confusion properties over the standard AES.

Modified AES Cipher Round and Key Schedule

The paper proposes a modification of the advanced encryption standard (AES) to address its high computational requirement steaming from the complex mathematical operations in the MixColumns Transformation which makes the encryption process slow. Bit Permutation was used instead of the MixColumns Transformation since the use of bit permutation in an encryption algorithm achieves efficiency by providing minimum encryption time and memory requirement. Results of the study showed that the modified AES algorithm exhibited faster encryption by 18.47% and faster decryption by 18.77% for text files. The modified AES algorithm also resulted to 16.53% higher avalanche effect compared with the standard AES thus improving the security performance. Application of the modified AES in encrypting images in Cipher Block Chaining mode showed that the modified algorithm also exhibited 16.88% faster encryption and 11.96% decryption compared with the standard AES. Likewise, modifying the algorithm achieved the ideal result in the histogram analysis, information entropy, the correlation coefficient of adjacent pixels to resist statistical attack.  The ideal value in number of pixels change rate and unified average change intensity were also achieved making the modified algorithm resistant to differential attack. These results show that modifying AES by using bit permutation to replace MixColumns Transformation was able to address the high computational requirement of the algorithm resulting in a faster and more secure encryption algorithm for text files and images .

/pdf/implementation-of-a-bit-permutation-based-advanced-1gmiz5by3o.pdf

Implementation of a bit permutation-based advanced encryption standard for securing text and image files

The transmission of a suitably compressed image over a bandwidth, over long distances, gives rise towards a new era in the field of information technology. A gradual increase in this appending scenic application, involving the transfer of the images securely over the Ethernet has become an increasingly important aspect to be addressed during thou phenomenon, especially in the transfer of the digital medical images vividly, encapsulated with abundant information related to these images. The compressed medical images of the DICOM format contain certain amount of confidential data, pertaining to a clinical research or to an individual, and the confidentiality of the same has to be preserved from various security threats and eves-dropping. With a widespread applications among various multimedia applicative systems, telemedicine, medical imaging, military and certain safety-critical applications, inter-net and intra-net communicative applications, etc, a reliable transfer of suitable information, efficiently & securely is considered as one of the revolutionary aims in today’s communication technology and visual cryptographic methodologies. Real-time applications as such detailed above majorly is concerned with the security measures and many algorithms have been developed as a proof for various visual cryptographic methodologies.
In this paper we propose an efficient and a reliable visual cryptographic methodology which focuses on the encryption and decryption of the two-dimensional DICOM standard compressed medical image, effectively.
This paper discusses an efficient design of 192 bit encoder using AES Rijndael Algorithm with the decomposition of an image into square image size blocks and the image blocks are shuffled using 2D CAT map.
The shuffling of the image blocks/pixels employs a Logistic map of these image pixels coupled with 2D mapping of the pixels of the DICOM standard medical image, generated randomly, being the control parameter thereby creating a confusion between the cipher and the plain image, gradually increasing the resistive factor against the significant attacks. This paper proposes various analytical metrics such as correlation analysis, 
entropy analysis, homogeneity analysis, energy analysis, contrast and mean of absolute deviation analysis, to evaluate the proposed algorithm, and their suitability in image encryption applications.

/pdf/a-naive-visual-cryptographic-algorithm-for-the-transfer-of-a-1eo5nqpicn.pdf

A Naïve Visual Cryptographic Algorithm for the Transfer of a Compressed Medical Images

The continuing advancement of technology had provided security issues in protecting the confidentiality of information. The need to protect unauthorized access of a third party is warranted.  In this paper, the reduced-round modified AES with revised round keys and key schedule is proposed to ensure file confidentiality.  The modifications to the AES cipher round was the reduction of the round iterations from 10 to 6, and additional key permutations were added in between states; while in the key schedule, additional byte substitution process was appended.  Time and throughput were utilized to measure the performance of the application's encryption/decryption process; while the avalanche effect and randomness tests were used to measure the security of the modified AES algorithm.  The results of evaluations have shown that the encryption and decryption time have improved by 1.27% and 1.21% respectively while the throughput has similarly improved by 1.29% and 3.19% for both encryption and decryption respectively.  Whereas the avalanche effect of the modified AES was 50.06% which was more than the ideal value of 50% and it was also better than the standard AES which was 49.94% using the sample dataset.  Finally, all the ciphertext outputs of the modified AES passed the randomness tests.

/pdf/file-encryption-based-on-reduced-round-aes-with-revised-3a70nzmdx4.pdf

File encryption based on reduced-round AES with revised round keys and key schedule

Cryptography is a scientific art which deals with the methods for changing over messages, data and information in some dynamically and haphazardly planned language of characters which are mixed up and not understandable for people or notwithstanding for a machine. While doing this, it is guaranteed that authorized frameworks and humans can recuperate the original message by validating their authentication. There are different calculations and strategies are proposed for cryptography purposes. This paper focuses on examination of two individual cryptographic calculation RSA and Blowfish, how they work and what will be the impact on security and speed if these two are converged into one hybrid calculation with appropriate modification. This paper presents the comparative analysis in terms of encryption and decryption time for individual as well as hybrid algorithm.

Enhancement of Security Using B-RSA Algorithm

Cryptography guarantees security in communication through encryption. This paper proposed a modified Blowfish encryption that uses 128-bit block size and 128-bit key to comply with minimum requirements as an encryption standard. The modification retained the original structure for easy migration but utilized two S-boxes to save memory. A derivation was added to prevent symmetry.  The algorithm’s performance was evaluated using time, and avalanche. Upon testing, the modified blowfish is slower with key, encryption, and decryption average of 26.99ms, 1651.83ms, and 2765.04ms compared to blowfish with 21.65ms, 1297.76ms and 2176.59ms due to block size difference. Applying 128-bit block size increases security by decreasing the chances of having duplicate blocks that may leak information. The modified Blowfish is faster compared to Twofish with an encryption and decryption average time of 2418.08ms and 4002.70ms. The added derivation improved the avalanche of the modified blowfish.  Blowfish achieved 47.14% while modified Blowfish attained 52.86%.

http://ijeecs.iaescore.com/index.php/IJEECS/article/download/11985/9298

Modified Blowfish Algorithm

EMR helped improve services to patients by delivering organization and accuracy of patient information, but issues regarding security breaches and medical identity theft are growing concerns This paper enhance the current EMR system by integrating modified encryption The simulation used modified Blowfish algorithm in an EMR system that focuses on four goals: 1) define the requirements, 2) design and identify features, 3) develop the EMR incorporating added security mechanism using modified Blowfish algorithm, and 4) test the application with sample data Based on the results, the incorporation of the encryption was successful based on testing and checking done on the input terminal and the database server Data inputted on the EMR system was successfully encrypted before transmission and decrypted only on the terminal for viewing Performance results show that without encryption, saving took an average of 878ms while encrypted, it acquired 888ms, a difference of 1ms can be noted The minimal difference is because of the size of the data The average decryption time of all records using modified algorithm took 1342ms while using plaintext took 1322ms The decryption time is higher by 20ms due to the application of the decryption algorithm

/pdf/securing-electronic-medical-records-using-modified-blowfish-pozx9gu42l.pdf

Theda Flare Ginoy Quilala

Papers

Modified Blowfish Algorithm

Securing Electronic Medical Records Using Modified Blowfish Algorithm