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Cryptography Threats
Published in Nicholas Kolokotronis, Stavros Shiaeles, Cyber-Security Threats, Actors, and Dynamic Mitigation, 2021
Konstantinos Limniotis, Nicholas Kolokotronis
Cryptanalysis is the study of mathematical techniques for attempting to defeat cryptographic techniques [1]. To assess the cryptographic strength of a cryptographic algorithm (also being called cipher), we assume specific capabilities of the attacker or cryptanalyst (regarding her/his knowledge, apart from the encryption algorithm itself); depending on these capabilities, specific general types of cryptanalytic attacks are determined. A ciphertext-only attack is the case which attacker tries to recover the decryption key or plaintext by only observing ciphertext. A known-plaintext attack is one where the attacker in addition knows a part of the plaintext or, more generally, some pairs “plaintext-ciphertext.” The chosen-plaintext attack assumes a more powerful attacker, being able to choose for which plaintexts she/he will be able to learn the corresponding ciphertexts2. In a converse manner, the chosen-ciphertext attack assumes that the attacker is able to choose for which ciphertexts she/he will be able to learn the corresponding plaintexts3.
Introduction
Published in Jonathan Katz, Yehuda Lindell, Introduction to Modern Cryptography, 2020
The first two types of attack are the easiest to carry out. In a ciphertext-only attack, the only thing the adversary needs to do is eavesdrop on the communication channel over which encrypted messages are sent. In a known-plaintext attack it is assumed the adversary also obtains ciphertexts corresponding to known plaintexts. This is often easy to accomplish because not all encrypted messages are secret, at least not indefinitely. As a trivial example, two parties may always encrypt a “hello” message whenever they begin communicating. As a more complex example, encryption may be used to keep quarterly-earnings reports secret until their release date; in this case, anyone eavesdropping on the ciphertext will later obtain the corresponding plaintext.
Phase Retrieval in Optical Cryptography
Published in S. Ramakrishnan, Cryptographic and Information Security, 2018
Naveen Kumar Nishchal, Areeba Fatima
DRPE has been a widely studied optical cryptosystem and its many variants have been reported. However, the encryption technique was shown to be vulnerable to the known plaintext attack [19]. In a known plaintext attack, the attacker knows the plaintext and the ciphertext and tries to retrieve the keys. This attack is based on the phase retrieval technique, and is described below:
Asymmetric encryption algorithm for colour images based on fractional Hartley transform
Published in Journal of Modern Optics, 2019
A. K. Yadav, Phool Singh, Indu Saini, Kehar Singh
In a known-plaintext attack (KPA), an intruder is assumed to possess a pair of plaintext–ciphertext, and has access to the encryption scheme. In the chosen-plaintext attack (CPA), the intruder has the freedom to select a plaintext and generate its ciphertext from the given scheme. In both KPA and CPA, the intruder attempts to retrieve the encryption (secret) keys. Due to non-linearity of phase-truncated operators, the proposed cryptosystem could be immune to KPA and CPA. Even if encryption keys are obtained for any pair of plaintext–ciphertext in KPA, these keys cannot be used for decrypting any ciphertext as the encryption keys are completely dependent on the plaintext and are treated as a one-time pad (63, 64). In a recent study (65), it has been shown that a plaintext can be retrieved even without the corresponding ciphertext, just on the basis of the decryption keys in the phase-truncated asymmetric cryptosystem. However, such a situation may not be truly feasible.