Abstract
This study proposes securing digital color images with hybrid substitution cryptographic methods combined with the Vigenere and Beaufort methods. The hybrid process is carried out using the help of two randomly generated keys. The first key is a matrix with an 8-bits value and the second key is a matrix with a binary value. The binary key is used to determine the Vigenere or Beaufort process, while the 8-bit key is used for modulus operations based on the Vigenere or Beaufort algorithm. At the test stage used a standard image that has an RGB color channel as a dataset. The quality of the cryptographic method is measured by several measuring instruments such as MSE, PSNR, and SSIM to determine the quality of encryption visually and the perfection of decryption, besides that it is used Entropy, NPCR and UACI to determine the probability of encryption resistance and quality against differential attacks. The TIC TOC function is also used to measure the computing speed of the encryption and decryption process. Measurement results using all measuring instruments indicate that the proposed method has very satisfying results and has fast computing. Keywords – Cryptography, Substitution Cipher, Modulus Function, Encryption, Decryption, Image Transmission
Highlights
Nowadays the digital multimedia landscape has changed due to the increasingly modern technology and many positive things and an unexpected problem related to the security of sending multimedia data in cyberspace
Encrypted images are tested for encryption quality using several gauges such as entropy, MSE, Peak values Signal to Noise Ratio (PSNR), Structural Similarity Index (SSIM), unified average change in intensity (UACI), and Number of Pixel Change Rate (NPCR)
MSE, PSNR, and SSIM are used to measure the quality of image encryption based on errors, noise, and structural changes in the image
Summary
Nowadays the digital multimedia landscape has changed due to the increasingly modern technology and many positive things and an unexpected problem related to the security of sending multimedia data in cyberspace. Cryptography is a study that is used to secure data by encoding the data. The process of coding data will change the form that can be random or become another form that has a different meaning from the original data so that the data cannot be read directly[1], [4], [5]. The encryption process and the decryption process are the two main processes in cryptography, where encryption is used to encode data while decryption is used to return the encoded data to its original form[6]
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