# Two-Layer Security Algorithms to Prevent Attacks on Data in Cyberspace
## 2 Literature Review  
[PERSON] et al. [1] modified the Vigenere cipher algorithm to secure data and prevent key identification from Kasiski tests, implemented the results obtained from the Vigenere cipher on the Polybius algorithm, and obtained the ciphertext. According to the researchers, when the data are key-based encrypted, if the attacker knows the algorithm used on these data, then the probability of obtaining this key can be determined by the Kasiski test, which is a problem. To solve this problem, the researchers first took the plaintext and implemented this plaintext on a key. When the key length was smaller than the plaintext, the key was repeated according to the length of the plaintext, and the length was found by applying the obtained ciphertext to the Kasiski test. The researchers modified the Vigenere cipher algorithm to solve the key length problem. Instead of repeating the key, they generated the key according to the length of the plaintext and obtained a text. Then, this text was implemented on the 5 \(\times\) 5 Polybius matrix to obtain the ciphertext. [PERSON], [PERSON] et al. [23] developed a hybrid cryptographic algorithm using the Vigenere cipher and Caesar cipher techniques to encrypt data. To convert the data from plaintext to ciphertext, the plaintext was first taken, the plaintext was added with the key for which the standard ASCII was used, and a Caesar text was obtained from the Caesar cipher. After obtaining the Ceaser text, the Ceaser ciphertext and key were implemented on the Vigenere cipher and the obtained ciphertext. After obtaining the ciphertext, the accuracy of the hybrid algorithm was checked through MATLAB simulation. After obtaining different results, the behavior of the three techniques was identified with the help of graphs, after which it was discussed that the present algorithm provides better efficiency than the other two algorithms. [PERSON] et al. [20] developed a new hybrid algorithm by combining the Polybius and Vigenere cipher. The novelty of this algorithm was implementing a double encryption mechanism on the data. First, a plaintext and a randomized key were implemented on the Vigenere cipher, and the encrypted text was obtained in an alphabetical form. Afterward, the Polybius mechanism was implemented on the alphabetic encrypted text in which the alphabets were converted to numbers, and a ciphertext was obtained. [PERSON] et al. [24] developed a hybrid algorithm to secure data in which email-based encryption and decryption were done between the sender and receiver. The hybrid algorithm was the combination of a Vigenere cipher and Polybius cipher in which encryption and decryption were performed with the same key. The data were encrypted and decrypted through a webpage. The webpage contained a textbox (sender email, password, message, and receiver email) and a button (encryption and decryption). First, the plaintext was taken and sent to the receiver by making this plaintext encrypted. The webpage used the textbox to convert the data from a non-readable format to a readable format, and the plaintext was obtained. [PERSON] et al. [25] developed the 95 \(\times\) 95 Vigenere cipher table by modifying the 26 \(\times\) 26 Vigenere cipher table, which consisted of numbers, alphabets, and special symbols. Each plaintext character was equalized to its equivalent ASCII in this algorithm. Afterward, a key was generated and repeated according to the existing length. Then, each key character and plaintext character was equalized to ASCII numerical values, and addition was performed. Mod-95 was taken based on the results obtained from addition, and a ciphertext was obtained. [PERSON] et al. [26] developed a modified algorithm by combining the Vigenere cipher and affine cipher, named the modified Vigenere cipher. First, a plaintext was taken, this plaintext was added with a key with the help of the Vigenere table, the encrypted value was obtained, and then the encrypted results were shifted to the ciphertext according to the length of the key.