Security of data (text, audio, and images) is becoming more complex with the increment in its amount. In order to upsurge the reliability, the captcha (Completely Automated Public Turing test to tell Computers and Humans Apart) is used to ensure authenticity. In contrast, even these captchas can be hacked and security can be easily impeached, aim of these captchas is to identify if the user is genuine or else if it is just a robot trying to spam the system. This paper presents auxiliary hybridization of AES and Blowfish cryptographic algorithms for image encipherment and decipherment. Here, AES is using Blowfish as its subroutine where Blowfish encrypts and decrypts the AES encoded image. This is then handed to AES for second level decryption. Here the image which is to be encrypted is applied to AES algorithm, its output is further used as an input for Blowfish algorithm. Output of this doubly encrypted image is then decrypted in the reverse order of encipherment. This auxiliary hybridization adds security to the image rendering it the capacity to become useful in highly important organizations. Private key cryptography uses single secret key at both, the sender and the receiver end. Using symmetric key cryptographic algorithm for this process makes the complete process fast and more secure in comparison to when asymmetric cryptographic algorithms are used for the same purpose. Moreover, symmetric key cryptographic algorithms are more suitable for larger files and images. These also help in maintaining the confidentiality of the data.
A New Symmetric Key Cryptographic Algorithm using Paley Graphs and ASCII Values
