Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

International Journal of Foundations of Computer Science

ENCRYPTION OF QUANTUM INFORMATION

Jan Bouda, Vladimír Bužek

Published Oct 1, 2003• 1 citation
Publisher

Abstract

We study in detail the problem of encryption of quantum information. We present an attack on a private quantum channel (PQC) which applies when partial classical description of a ciphertext is known (the so-called known-ciphertext attack) and we show how this situation can be avoided. The quantum analogue of the known plaintext attack is also discussed. We determine how correlations between quantum systems can be encrypted and we conclude that two PQCs on the subsystems form a PQC on the whole composite system. Finally, some applications of the PQC are suggested and a security of a noisy channel is discussed.

DOI
10.1142/s012905410300200x

Related papers

Security of the private quantum channel

Jan Bouda, Vladimír Bužek

We extensively discuss the problem of encryption of quantum information. We present an attack on the private quantum channel which applies when partial classical description of the cipher text is known (the known-ciphertext attack) and show how to avoid this situation. The quantum analogue of the known-plaintext attack is also discussed.

Journal of Modern Optics•Jan 1, 2003•3 citations

Exact and approximate encryption of quantum information

Jan Bouda

In this paper, we address properties of the private quantum channel (PQC), namely a security weakness occurring when at least two copies of the ciphertext are available. We discuss possible definitions of the known-plaintext, known-ciphertext and chosen-plaintext attack. We examine the ability of a PQC to randomize correlations and, finally, we show that specific PQCs encrypting a given set of plaintexts can achieve the approximate encryption of a larger set of plaintexts.

•Jan 1, 2005•0 citations

Quantum Encryption with Certified Deletion

Islam, Rabib

In the context of classical information, every message is composed of 0s and 1s; these messages can generally be copied at will. However, when quantum phenomena are used to model information, this guarantee no longer exists. This difference gives rise to a range of cryptographic possibilities when one considers encoding certain messages as quantum information. In our case, we analyze a potential benefit of encoding part of an encryption scheme’s ciphertext as quantum information. We call this type of ciphertext a quantum ciphertext. In particular, quantum ciphertexts are useful when one wants to be able to prove the deletion of the plaintext underlying a ciphertext. Since classical ciphertexts can be copied, clearly such feat is impossible using classical information alone. However, we show that quantum encodings allow such certified deletion. More precisely, we show that it is possible to encrypt classical data into a quantum ciphertext such that the recipient of the ciphertext can produce a classical string which proves to the originator that the recipient has relinquished any chance of recovering the plaintext, should the decryption key be revealed. Our scheme is feasible with current quantum technology: the honest parties only require quantum devices for single-qubit preparation and measurements, and the scheme is robust against noise in these devices. Furthermore, we provide a proof of security which requires only a finite amount of communication, and which therefore avoids the common technique of relying on the analysis of an asymptotic case.

•Jan 20, 2020•39 citations

A Quantum-Classical Scheme towards Quantum Functional Encryption

Aditya Ahuja

Quantum encryption is a well studied problem for both classical and quantum information. However, little is known about quantum encryption schemes which enable the user, under different keys, to learn different functions of the plaintext, given the ciphertext. In this paper, we give a novel one-bit secret-key quantum encryption scheme, a classical extension of which allows different key holders to learn different length subsequences of the plaintext from the ciphertext. We prove our quantum-classical scheme secure under the notions of quantum semantic security, quantum entropic indistinguishability, and recent security definitions from the field of functional encryption.

arXiv:1703.00207•Mar 1, 2017•0 citations

Optimality of private quantum channels

Jan Bouda, Mário Ziman

We addressed the question of optimality of private quantum channels. We have shown that the Shannon entropy of the classical key necessary to securely transfer the quantum information is lower bounded by the entropy exchange of the private quantum channel $\cal E$ and von Neumann entropy of the ciphertext state $\varrho^{(0)}$. Based on these bounds we have shown that decomposition of private quantum channels into orthogonal unitaries (if exists) is optimizing the entropy. For non-ancillary single qubit PQC we have derived the optimal entropy for arbitrary set of plaintexts. In particular, we have shown that except when the (closure of the) set of plaintexts contains all states, one bit key is sufficient. We characterized and analyzed all the possible single qubit private quantum channels for arbitrary set of plaintexts. For the set of plaintexts consisting of all qubit states we have characterized all possible approximate private quantum channels and we have derived the relation between the security parameter and the corresponding minimal entropy.

arXiv:0710.2004•Journal of Physics A Mathematical and Theoretical•Apr 30, 2007•10 citations

On the Key-Uncertainty of Quantum Ciphers and the Computational Security of One-way Quantum Transmission

Ivan Damgaard, Thomas B. Pedersen, Louis Salvail

We consider the scenario where Alice wants to send a secret (classical) $n$-bit message to Bob using a classical key, and where only one-way transmission from Alice to Bob is possible. In this case, quantum communication cannot help to obtain perfect secrecy with key length smaller then $n$. We study the question of whether there might still be fundamental differences between the case where quantum as opposed to classical communication is used. In this direction, we show that there exist ciphers with perfect security producing quantum ciphertext where, even if an adversary knows the plaintext and applies an optimal measurement on the ciphertext, his Shannon uncertainty about the key used is almost maximal. This is in contrast to the classical case where the adversary always learns $n$ bits of information on the key in a known plaintext attack. We also show that there is a limit to how different the classical and quantum cases can be: the most probable key, given matching plain- and ciphertexts, has the same probability in both the quantum and the classical cases. We suggest an application of our results in the case where only a short secret key is available and the message is much longer.

arXiv:quant-ph/0407066•Jul 8, 2004•1 citation
We study in detail the problem of encryption of quantum information. We present an attack on a private quantum channel (PQC) which applies when partial classical description of a ciphertext is known (the so-called known-ciphertext attack) and we show how this situation can be avoided. The quantum analogue of the known plaintext attack is also discussed. We determine how correlations between quantum systems can be encrypted and we conclude that two PQCs on the subsystems form a PQC on the whole composite system. Finally, some applications of the PQC are suggested and a security of a noisy channel is discussed.
In the context of classical information, every message is composed of 0s and 1s; these messages can generally be copied at will. However, when quantum phenomena are used to model information, this guarantee no longer exists. This difference gives rise to a range of cryptographic possibilities when one considers encoding certain messages as quantum information. In our case, we analyze a potential benefit of encoding part of an encryption scheme’s ciphertext as quantum information. We call this type of ciphertext a quantum ciphertext. In particular, quantum ciphertexts are useful when one wants to be able to prove the deletion of the plaintext underlying a ciphertext. Since classical ciphertexts can be copied, clearly such feat is impossible using classical information alone. However, we show that quantum encodings allow such certified deletion. More precisely, we show that it is possible to encrypt classical data into a quantum ciphertext such that the recipient of the ciphertext can produce a classical string which proves to the originator that the recipient has relinquished any chance of recovering the plaintext, should the decryption key be revealed. Our scheme is feasible with current quantum technology: the honest parties only require quantum devices for single-qubit preparation and measurements, and the scheme is robust against noise in these devices. Furthermore, we provide a proof of security which requires only a finite amount of communication, and which therefore avoids the common technique of relying on the analysis of an asymptotic case.
Quantum encryption is a well studied problem for both classical and quantum information. However, little is known about quantum encryption schemes which enable the user, under different keys, to learn different functions of the plaintext, given the ciphertext. In this paper, we give a novel one-bit secret-key quantum encryption scheme, a classical extension of which allows different key holders to learn different length subsequences of the plaintext from the ciphertext. We prove our quantum-classical scheme secure under the notions of quantum semantic security, quantum entropic indistinguishability, and recent security definitions from the field of functional encryption.
We addressed the question of optimality of private quantum channels. We have shown that the Shannon entropy of the classical key necessary to securely transfer the quantum information is lower bounded by the entropy exchange of the private quantum channel E\cal EE and von Neumann entropy of the ciphertext state ϱ(0)\varrho^{(0)}ϱ(0). Based on these bounds we have shown that decomposition of private quantum channels into orthogonal unitaries (if exists) is optimizing the entropy. For non-ancillary single qubit PQC we have derived the optimal entropy for arbitrary set of plaintexts. In particular, we have shown that except when the (closure of the) set of plaintexts contains all states, one bit key is sufficient. We characterized and analyzed all the possible single qubit private quantum channels for arbitrary set of plaintexts. For the set of plaintexts consisting of all qubit states we have characterized all possible approximate private quantum channels and we have derived the relation between the security parameter and the corresponding minimal entropy.
We consider the scenario where Alice wants to send a secret (classical) nnn-bit message to Bob using a classical key, and where only one-way transmission from Alice to Bob is possible. In this case, quantum communication cannot help to obtain perfect secrecy with key length smaller then nnn. We study the question of whether there might still be fundamental differences between the case where quantum as opposed to classical communication is used. In this direction, we show that there exist ciphers with perfect security producing quantum ciphertext where, even if an adversary knows the plaintext and applies an optimal measurement on the ciphertext, his Shannon uncertainty about the key used is almost maximal. This is in contrast to the classical case where the adversary always learns nnn bits of information on the key in a known plaintext attack. We also show that there is a limit to how different the classical and quantum cases can be: the most probable key, given matching plain- and ciphertexts, has the same probability in both the quantum and the classical cases. We suggest an application of our results in the case where only a short secret key is available and the message is much longer.