115 research outputs found
Revocable quantum timed-release encryption
Timed-release encryption is a kind of encryption scheme that a
recipient can decrypt only after a specified amount of time T
(assuming that we have a moderately precise estimate of his computing
power). A revocable timed-release encryption is one where,
before the time T is over, the sender can give back the
timed-release encryption, provably loosing all access to the data. We
show that revocable timed-release encryption without trusted parties
is possible using quantum cryptography (while trivially impossible
classically).
Along the way, we develop two proof techniques in the quantum random
oracle model that we believe may have applications also for other
protocols.
Finally, we also develop another new primitive, unknown recipient
encryption, which allows us to send a message to an
unknown/unspecified recipient over an insecure network in such a way
that at most one recipient will get the message
Quantum Encryption with Certified Deletion: Public Key and Attribute-Based
Broadbent and Islam (TCC \u2720) proposed a quantum cryptographic primitive called quantum encryption with certified deletion. In this primitive, a receiver in possession of a quantum ciphertext can generate a classical certificate that the encrypted message is deleted. Though they proved that their construction is information theoretically secure, a drawback is that the construction is limited to the setting of one-time symmetric key encryption (SKE) where a sender and receiver have to share a common key in advance and the key can be used only once.
In this paper, we construct a (reusable-key) public key encryption (PKE) and attribute-based encryption (ABE) with certified deletion. Our PKE with certified deletion is constructed assuming the existence of IND-CPA secure PKE, and our ABE with certified deletion is constructed assuming the existence of indistinguishability obfuscation and one-way function
Making Existential-Unforgeable Signatures Strongly Unforgeable in the Quantum Random-Oracle Model
Strongly unforgeable signature schemes provide a more stringent security
guarantee than the standard existential unforgeability. It requires that not
only forging a signature on a new message is hard, it is infeasible as well to
produce a new signature on a message for which the adversary has seen valid
signatures before. Strongly unforgeable signatures are useful both in practice
and as a building block in many cryptographic constructions.
This work investigates a generic transformation that compiles any
existential-unforgeable scheme into a strongly unforgeable one, which was
proposed by Teranishi et al. and was proven in the classical random-oracle
model. Our main contribution is showing that the transformation also works
against quantum adversaries in the quantum random-oracle model. We develop
proof techniques such as adaptively programming a quantum random-oracle in a
new setting, which could be of independent interest. Applying the
transformation to an existential-unforgeable signature scheme due to Cash et
al., which can be shown to be quantum-secure assuming certain lattice problems
are hard for quantum computers, we get an efficient quantum-secure strongly
unforgeable signature scheme in the quantum random-oracle model.Comment: 15 pages, to appear in Proceedings TQC 201
Weakening Assumptions for Publicly-Verifiable Deletion
We develop a simple compiler that generically adds publicly-verifiable
deletion to a variety of cryptosystems. Our compiler only makes use of one-way
functions (or one-way state generators, if we allow the public verification key
to be quantum). Previously, similar compilers either relied on the use of
indistinguishability obfuscation (Bartusek et. al., ePrint:2023/265) or
almost-regular one-way functions (Bartusek, Khurana and Poremba,
arXiv:2303.08676).Comment: 13 pages. arXiv admin note: text overlap with arXiv:2303.0867
Depth-Bounded Quantum Cryptography with Applications to One-Time Memory and More
With the power of quantum information, we can achieve exciting and classically impossible cryptographic primitives. However, almost all quantum cryptography faces extreme difficulties with the near-term intermediate-scale quantum technology (NISQ technology); namely, the short lifespan of quantum states and limited sequential computation. At the same time, considering only limited quantum adversaries may still enable us to achieve never-before-possible tasks.
In this work, we consider quantum cryptographic primitives against limited quantum adversaries - depth-bounded adversaries. We introduce a model for (depth-bounded) NISQ computers, which are classical circuits interleaved with shallow quantum circuits. Then, we show one-time memory can be achieved against any depth-bounded quantum adversaries introduced in the work, with their depth being any pre-fixed polynomial. Therefore we obtain applications like one-time programs and one-time proofs. Finally, we show our one-time memory has correctness even against constant-rate errors
Limitations on Uncloneable Encryption and Simultaneous One-Way-to-Hiding
We study uncloneable quantum encryption schemes for classical messages as
recently proposed by Broadbent and Lord. We focus on the information-theoretic
setting and give several limitations on the structure and security of these
schemes: Concretely, 1) We give an explicit cloning-indistinguishable attack
that succeeds with probability where is related to the
largest eigenvalue of the resulting quantum ciphertexts. 2) For a uniform
message distribution, we partially characterize the scheme with the minimal
success probability for cloning attacks. 3) Under natural symmetry conditions,
we prove that the rank of the ciphertext density operators has to grow at least
logarithmically in the number of messages to ensure uncloneable security. 4)
The \emph{simultaneous} one-way-to-hiding (O2H) lemma is an important technique
in recent works on uncloneable encryption and quantum copy protection. We give
an explicit example which shatters the hope of reducing the multiplicative
"security loss" constant in this lemma to below 9/8.Comment: v2 and v3: several fixes, including a missing attribution to
Broadbent and Lor
Weakening Assumptions for Publicly-Verifiable Deletion
We develop a simple compiler that generically adds publicly-verifiable deletion to a variety of cryptosystems. Our compiler only makes use of one-way functions (or one-way state generators, if we allow the public verification key to be quantum). Previously, similar compilers either relied on the use of indistinguishability obfuscation (Bartusek et. al., ePrint:2023/265) or almost-regular one-way functions (Bartusek, Khurana and Poremba, arXiv:2303.08676)
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