";s:4:"text";s:10291:" The 500 sequences are generated by the method described in Section 2.3. Autocorrelation test checks the degree of dependence between a sequence ( and its shifted sequence [27]. In the following sections, the results of the statistical tests for the KSAs are discussed. The authors also claimed to reduce the code size of the overall block cipher. The time of one execution for KSA can be used for comparison between KSAs. KSAs of Serpent and Twofish have good independence among the subkeys which can make ciphers more immune against the cryptanalysis attacks related to KSA. Therefore, it is proposed that a KSA may at least be tested against these properties. From Table 3, it can be seen that the SAC values of the KSA lie on the x-axis. The results confirm that the proposed criterion can effectively differentiate between strong- and weak-key schedule algorithms. %%EOF
A function of n input bits maps into output bits is said to be complete, if each output bit depends upon all input bits [28]; that is. In BUCT, 500-random secret key set is taken. From Table 3, it can be observed that the SAC value of the KSA of Serpent is approximately equal to 1 for each round subkey. The number of the nonrandom secret keys in high and low density is 8257. This complex relationship leads the cipher strong against many cryptanalysis attacks which utilizes the avalanche weakness in KSA. Each KSA is implemented in C language and the CPU speed is 3.00 GHz. Vladescu, and L. Gheorghe, “Randomness evaluation framework of cryptographic algorithms,”, D. Rane Deepali, “Superiority of twofish over blowfish,”, E. Biham, O. Dunkelman, and N. Keller, “A new attack on 6-round IDEA,” in, J. C. Hernandez-Castro, P. Peris-Lopez, and J. P. Aumasson, “On the key schedule strength of present,” in, J. Huang, S. Vaudenay, and X. Lai, “On the key schedule of lightweight block ciphers,” in, O. Özen, K. Varıcı, C. Tezcan, and Ç. Kocair, “Lightweight block ciphers revisited: cryptanalysis of reduced round PRESENT and HIGHT,” in, R. Saha, G. Geetha, G. Kumar, and T. H. Kim, “RK-AES: an improved version of AES using a new key generation process with random keys,”, M. Rafighi and N. Moatazedi, “Optimization of IDEA key-schedule algorithm for safe use in cloud,”, E. Biham, O. Dunkelman, and N. Keller, “New cryptanalytic results on IDEA,” in. Here, is a subkey set, is the key schedule algorithm function, is the secret key to length -bits, is the length of subkeys, and is the number of subkeys. A week key schedule algorithm makes a strong cipher vulnerable to many statistical and other cryptanalysis attacks.
For each round, the subkeys of KSA of AES pass the frequency test with a value greater than 98%. The authors declare that they have no conflicts of interest. For this purpose, high- and low-density keys are selected and used as secret keys in the KSAs. As indicated in Table 4, the results of the KSAs of PRESENT show that the passing percentage value is zero for both high- and low-density keys in the case of PRESENT; that is, no sequence passes the statistical tests. The low-density keys are the set of secret keys in which one and two bits of the secret keys are 1, whereas other bits are zero. Here, , , , and (Ki [L] ⊕ Kj) is the XOR between the Lth byte of with all bits of . Related-key attacks and slide attacks take the advantage of this simple relationship between the subkeys and secret key. Many studies have been performed on the cryptographic strength evaluation of the encryption algorithms; however, strength evaluation of the key schedule algorithms often obtains less attention that can lead towards the possible loophole in the overall encryption process. Also, KSA of AES has few nonlinear elements and slower diffusion structure to generate the subkeys. The above studies reflect that the evaluation of the KSA during its design stage has been the less focused area in the literature. The subkey length used in the round function for these algorithms is different but for comparison purpose we took all the key lengths equal to 128 bits. We will be providing unlimited waivers of publication charges for accepted research articles as well as case reports and case series related to COVID-19. 1024 0 obj
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The purpose of this set of tests is to evaluate the strength of KSA when the secret key is nonrandom. Studies show that although statistical tests are not the sufficient criteria for claiming the cryptographic strength of the cryptographic algorithms, however, it provides necessary criteria for a strong cryptographic algorithm. The execution time for KSA of PRESENT is 0.0001 seconds to generate 11 subkeys, whereas IDEA-KSA takes 0 seconds to generate the same number of subkeys.
Two statistical tests, namely, frequency test and Strict Avalanche Criteria (SAC) of the CryptX test suite, were used to measure the strength of KSA of AES. Triple DES was designed to replace the original Data Encryption Standard (DES) algorithm, which hackers eventually learned to defeat with relative ease. In this paper, we define a Key Schedule Evaluation Criterion (KSEC) that can evaluate the cryptographic properties such as confusion, diffusion, randomness, and independence among subkeys. The description of selected cryptographic sets of tests is given in the following sections. Cryptographic Strength Evaluation of Key Schedule Algorithms, Riphah Institute of Systems Engineering, Riphah International University, Rawalpindi, Pakistan, Department of Computer Science, Bahauddin Zakariya University, Multan, Pakistan, College of Community, Taibah University, Medina, Saudi Arabia, Department of Computer Science, COMSATS University Islamabad, Vehari Campus, Vehari, Pakistan, https://csrc.nist.gov/News/2017/Update-to-Current-Use-and-Deprecation-of-TDEA, https://docs.microsoft.com/en-us/microsoft-365/compliance/technical-reference-details-about-encryption, C. Li, F. Zhao, C. Liu, L. Lei, and J. Zhang, “A hyperchaotic color image encryption algorithm and security analysis,”, A. Biryukov and D. Khovratovich, “Related-key cryptanalysis of the full AES-192 and AES-256,” in, U. Blumenthal and S. M. Bellovin, “A better key schedule for DES-like ciphers,” in, L. R. Knudsen and J. E. Mathiassen, “On the role of key schedules in attacks on iterated ciphers,” in, L. R. Knudsen, “Practically secure Feistel ciphers,” in, J. Kelsey, S. Bruce, and W. David, “Key-schedule cryptanalysis of IDEA, G-DES, GOST, SAFER, and TRIPLE-DES,” in, L. May, M. Henricksen, W. Millan, G. Carter, and E. Dawson, “Strengthening the key schedule of the AES,” in, S. Afzal, U. Waqas, A. M. Mubeen, and M. Yousaf, “Statistical analysis of key schedule algorithms of different block ciphers,”, M. K. Pehlivanoğlu, M. T. Sakalli, N. Duru, and F. B. Sakalli, “The new approach of AES key schedule for lightweight block ciphers,”, J. Daemen, G. René, and V. Joos, “Weak keys for IDEA,” in, A. Bogdanov, L. R. Knudsen, G. Leander et al., “PRESENT: an ultra-lightweight block cipher,” in, B. Schneier, J. Kelsey, D. Whiting, D. Wagner, C. Hall, and N. Ferguson, “Twofish: a 128-bit block cipher,”, J. Daemen and V. Rijmen, “The design of Rijndael,” in, J. Huang, Y. Hailun, and L. Xuejia, “Transposition of AES key schedule,” in, S. Sulaiman, Z. Muda, J. Juremi, R. Mahmod, and S. M. Yasin, “A new shift column transformation: an enhancement of Rijndael key scheduling,”, A. Ross, B. Eli, and K. Lars, “Serpent: a proposal for the advanced encryption standard,” in, S. Fluhrer, I. Mantin, and A. Shamir, “Weaknesses in the key scheduling algorithm of RC4,” in, Y. Harmouch and R. El Kouch, “The benefit of using chaos in key schedule algorithm,”, R. E. J. Paje, A. M. Sison, and R. P. Medina, “Multidimensional key RC6 algorithm,” in, E. Simion, “The relevance of statistical tests in cryptography,”, C. H. Kim, “Improved differential fault analysis on AES key schedule,”. SSL/TLS Certificates most commonly use RSA keys and the recommended size of these keys keeps increasing (e.g. ASD has approved the following cryptographic algorithms for the protection of highly classified information when used in an evaluated implementation. Cryptographic algorithms are sequences of processes, or rules, used to encipher and decipher messages in a cryptographic system. A new Key Schedule Evaluation Criterion (KSEC) has been proposed to evaluate the cryptographic strength of any KSA. Table 5 presents the comparison of execution time between the KSAs. The value of can be changed according to the requirement. The KSAs of AES, Serpent, PRESENT, IDEA, and Twofish are selected and analyzed through the proposed criterion. A balance and uniformly distributed sequence makes the statistical attacks more complex.