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Private-Key Encryption
Published in Jonathan Katz, Yehuda Lindell, Introduction to Modern Cryptography, 2020
A pseudorandom generator provides a natural way to construct a secure, fixed-length encryption scheme with a key shorter than the message. Recall that in the one-time pad (see Section 2.2), encryption is done by XORing a random pad with the message. The crucial insight is that we can use a pseudorandom pad instead. Rather than sharing this long, pseudorandom pad, however, the sender and receiver can instead share a uniform seed that is used to generate the pad when needed (see Figure 3.2); this seed will be shorter than the pad and hence shorter than the message. As for security, the intuition is that a pseudorandom string “looks random” to any polynomial-time adversary and so a computationally bounded eavesdropper cannot distinguish between a message encrypted using the one-time pad or a message encrypted using this “pseudo-”one-time pad encryption scheme.
Security: Basics and Security Analytics
Published in Rakesh M. Verma, David J. Marchette, Cybersecurity Analytics, 2019
Rakesh M. Verma, David J. Marchette
The one-time padencryption!one time pad is a special kind of Vernam cipher in which the key is a random sequence as long as the message. It is best explained using a bit encoding of messages. Imagine that the plaintext message is the bit sequence: 0110101 and the key is the random sequence: 1101001. Then, the ciphertext sequence is obtained by bit-wise exclusive-or of the key and the plaintext, 1011100. As long as the key is a truly random sequence and as long as the message, the one-time pad provides what is called unconditional security. However, the one-time pad is not a practical cipher scheme since generating truly random long sequences is very difficult,4 the key must be different for different messages (hence the name one-time pad), and one also needs a secure mechanism for sharing the key.
Overview of Cryptography
Published in Alfred J. Menezes, Paul C. van Oorschot, Scott A. Vanstone, Handbook of Applied Cryptography, 2018
Alfred J. Menezes, Paul C. van Oorschot, Scott A. Vanstone
The one-time pad can be shown to be theoretically unbreakable. That is, if a cryptanalyst has a ciphertext string c1c2 · · · ct encrypted using a random key string which has been used only once, the cryptanalyst can do no better than guess at the plaintext being any binary string of length t (i.e., t-bit binary strings are equally likely as plaintext). It has been proven that to realize an unbreakable system requires a random key of the same length as the message. This reduces the practicality of the system in all but a few specialized situations. Reportedly until very recently the communication line between Moscow and Washington was secured by a one-time pad. Transport of the key was done by trusted courier.
Validation of Covert Cognizance Active Defenses
Published in Nuclear Science and Engineering, 2021
Arvind Sundaram, Hany Abdel-Khalik
We posit that this is extremely unlikely given the huge size of the nonobservable space for most complex systems, and the use of randomized techniques for signature insertion, rendering a level of security that matches the Vernam-Cipher gold standard. The Vernam Cipher, commonly known as a one-time pad, is a cipher that encrypts a message using a random key (pad) and can only be decrypted using this key. Its strength is derived from Shannon’s notion of perfect secrecy8 and requires the key to be truly random and nonreusable (one time). To demonstrate this, this paper will validate the implementation of C2 using sophisticated AI tools such as long short-term memory (LSTM) neural networks9 and the generative adversarial learning [generative adversarial networks (GANs)] framework,10 both using a supervised learning setting, i.e., by assuming that the AI training phase can distinguish between original data and the data containing the embedded signatures. While this is an unlikely scenario, it is assumed to demonstrate the resilience of the C2 signatures to discovery by AI techniques.
A computational journey in the true north
Published in International Journal of Parallel, Emergent and Distributed Systems, 2020
In recent years, I turned to quantum cryptography, a research and implementation field, in which Canada has a rightful claim of being a front runner, with cutting edge work being performed from coast to coast. At Queen's University, Dr. Marius Nagy, Dr. Naya Nagy, and I proved that, contrary to established belief, authentication between two parties, for cryptographic purposes, can be performed through purely quantum means [72]. Our quantum key distribution protocols produce secret information using public information only, something which was thought to be impossible for any cryptosystem [73–76]. We have also provided, for the first time, quantum cryptographic solutions to the problems of security and identity protection in wireless sensor networks [77, 78], multilevel security in hierarchical systems [79], and coping with decoherence [80], as well as exposing a less well known aspect of quantum cryptography [81]. Using our previous result on one-time pads [82], Dr. Naya Nagy, Dr. Marius Nagy, and I showed that secret information can be shared or passed from a sender to a receiver even if not encoded in a secret message. No parts of the original secret information ever travel via communication channels between the source and the destination. No encoding/decoding key is ever used. The two communicating partners, are endowed with coherent qubits that can be read and set while keeping their quantum values over time. Also, no classical communication channel used need be authenticated. This cryptosystem is, in some sense, the ‘book cipher’ approach to cryptography, revisited with a quantum twist. Furthermore, as each piece of secret information has a distinct public encoding, the cryptosystem is equivalent to a one-time pad, and as such is provably unbreakable [83].