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Cryptography Threats
Published in Nicholas Kolokotronis, Stavros Shiaeles, Cyber-Security Threats, Actors, and Dynamic Mitigation, 2021
Konstantinos Limniotis, Nicholas Kolokotronis
The operation in Figure 4.3, the Electronic Code Book (ECB) mode of operation, is not the most frequently used operation for block ciphers, due to a main disadvantage: pairwise identical plaintext blocks produce pairwise identical ciphertext blocks. Several other modes of operation have been standardized, alleviating this issue and also having many other desirable properties. We shall focus here on two of them: The Cipher Block Chaining (CBC) mode of operation (Figure 4.4) follows a chaining mode so as to ensure that the encryption of one plaintext block also depends on the previous ciphertext block. Therefore, even if two plaintext blocks are identical, the corresponding ciphertexts will be pairwise different. Note that an error in reception of one ciphertext block affects also the proper decryption of both the current and the subsequent ciphertext block, but no others. Moreover, in this mode of operation, an Initialization Vector (IV), of size equal to the block size of the algorithm, is necessary for starting the encryption of the first plaintext block (and, of course, for decrypting the first ciphertext block). The IV actually transforms a block cipher in a probabilistic (instead of deterministic) nature, since encrypting the same plaintext with the same key gives rise to a different ciphertext, under the assumption that the IV is being changed (which is an important security requirement for the IV—i.e. the IV should not reused under the same key).
Symmetric Algorithms I
Published in Khaleel Ahmad, M. N. Doja, Nur Izura Udzir, Manu Pratap Singh, Emerging Security Algorithms and Techniques, 2019
Faheem Syeed Masoodi, Mohammad Ubaidullah Bokhari
The objective here is to overcome the limitations faced in ECB mode by chaining together the encryption of all blocks in a way that each cipher block is reliant on the respective plaintext block as well as all preceding plaintext blocks. The underlying idea is to feedback the previously generated ciphertext as input to the algorithm and XOR it with next message block, which is then encrypted to generate next ciphertext block and it continues till all the message blocks are encrypted. Pertinently no ciphertext for feedback is available here for the first message block. CBC mode takes care of this by adding an IV to the first message block. The initialization vector is a randomized seed value and plays a vital role in making CBC encryption random.
Securing personal data in public cloud
Published in Journal of Information and Telecommunication, 2020
Péter Vörös, Dániel Csubák, Péter Hudoba, Attila Kiss
CrypStore PI is able to handle multiple users and multiple service providers for each user. Let m be the number of the users and be the number of different service providers for user . and are the encryption and decryption methods while (that can be the key and initialization vector packed together) is the encryption key used for user i. (Algorithm 1) and (Algorithm 2) are the methods used by CrypStore PI to store and to retrieve data from the storage.Explanation of UPLOAD() functionData: FileToUpload, UserIdResult: The encrypted file is split, the encrypted pieces are uploaded to the appropriate server the number of services for UserIdfori in 1..serviceNumdoExplanation of DOWNLOAD() functionData: FileToDownload, UserIdResult: Encrypted file pieces are downloaded from the servers, the pieces are joined together, and decryptedserviceNum := get the number of services for UserIdfori in 1..serviceNumdoReturn