A Crypto-Stegano Hybrid Application on Spatial Domain
Hüseyin Bilal MACİT · Bayburt Üniversitesi Fen Bilimleri Dergisi · 2022
The need for data security in communication is increasing with the developing technology. The best way to ensure data security is cryptography. Humanity has proposed many cryptography methods for hundreds of years. Today, there are complex cryptography algorithms, which are quite secure but require high processing power. Cryptography techniques used in the past are less secure but require less processing power. This article proposes an extended version of the Vigenère cipher, which is an ancient encryption method. Extended Vigenère cipher is able to encrypt upper and lower case letters, numeric characters, and punctuation marks. In addition, the method can use upper and lower case letters, numeric characters and punctuation marks as encryption key, and there is no key length limit. The cipher text generated with the extended Vigenère cipher is also hidden in an image to keep it safe in the transmission medium. Hiding is performed with LSB steganography, which is another data security method. Thus, both the readability and detectability of confidential data are reduced. The cryptological security of the proposed method is measured by the Avalanche effect. Steganographic safety is evaluated with SSIM and PSNR measurements. A user graphical interface has been developed and the maximum payload of the carrier image is measured before encryption. Proposed method applied on some test images with different specifications. 1 bit key modification avalanche effect results of proposed method with random plain texts between 1000-10000 characters with a key length of 8 and 16 characters is close to 50%. Also, SSIM value calculated over 0.99 each time while maximum steganographic payload of the test images reached.