1,572 research outputs found
Quantum Tokens for Digital Signatures
The fisherman caught a quantum fish. "Fisherman, please let me go", begged
the fish, "and I will grant you three wishes". The fisherman agreed. The fish
gave the fisherman a quantum computer, three quantum signing tokens and his
classical public key. The fish explained: "to sign your three wishes, use the
tokenized signature scheme on this quantum computer, then show your valid
signature to the king, who owes me a favor".
The fisherman used one of the signing tokens to sign the document "give me a
castle!" and rushed to the palace. The king executed the classical verification
algorithm using the fish's public key, and since it was valid, the king
complied.
The fisherman's wife wanted to sign ten wishes using their two remaining
signing tokens. The fisherman did not want to cheat, and secretly sailed to
meet the fish. "Fish, my wife wants to sign ten more wishes". But the fish was
not worried: "I have learned quantum cryptography following the previous story
(The Fisherman and His Wife by the brothers Grimm). The quantum tokens are
consumed during the signing. Your polynomial wife cannot even sign four wishes
using the three signing tokens I gave you".
"How does it work?" wondered the fisherman. "Have you heard of quantum money?
These are quantum states which can be easily verified but are hard to copy.
This tokenized quantum signature scheme extends Aaronson and Christiano's
quantum money scheme, which is why the signing tokens cannot be copied".
"Does your scheme have additional fancy properties?" the fisherman asked.
"Yes, the scheme has other security guarantees: revocability, testability and
everlasting security. Furthermore, if you're at sea and your quantum phone has
only classical reception, you can use this scheme to transfer the value of the
quantum money to shore", said the fish, and swam away.Comment: Added illustration of the abstract to the ancillary file
Quantum Tokens for Digital Signatures
The fisherman caught a quantum fish. Fisherman, please let me go , begged the fish, and I will grant you three wishes . The fisherman agreed. The fish gave the fisherman a quantum computer, three quantum signing tokens and his classical public key. The fish explained: to sign your three wishes, use the tokenized signature scheme on this quantum computer, then show your valid signature to the king, who owes me a favor .
The fisherman used one of the signing tokens to sign the document give me a castle! and rushed to the palace. The king executed the classical verification algorithm using the fish\u27s public key, and since it was valid, the king complied.
The fisherman\u27s wife wanted to sign ten wishes using their two remaining signing tokens. The fisherman did not want to cheat, and secretly sailed to meet the fish. Fish, my wife wants to sign ten more wishes . But the fish was not worried: I have learned quantum cryptography following the previous story (The Fisherman and His Wife by the brothers Grimm). The quantum tokens are consumed during the signing. Your polynomial wife cannot even sign four wishes using the three signing tokens I gave you .
How does it work? wondered the fisherman. Have you heard of quantum money? These are quantum states which can be easily verified but are hard to copy. This tokenized quantum signature scheme extends Aaronson and Christiano\u27s quantum money scheme, which is why the signing tokens cannot be copied .
Does your scheme have additional fancy properties? the fisherman asked. Yes, the scheme has other security guarantees: revocability, testability and everlasting security. Furthermore, if you\u27re at sea and your quantum phone has only classical reception, you can use this scheme to transfer the value of the quantum money to shore , said the fish, and swam away
Quantum Prudent Contracts with Applications to Bitcoin
Smart contracts are cryptographic protocols that are enforced without a
judiciary. Smart contracts are used occasionally in Bitcoin and are prevalent
in Ethereum. Public quantum money improves upon cash we use today, yet the
current constructions do not enable smart contracts. In this work, we define
and introduce quantum payment schemes, and show how to implement prudent
contracts -- a non-trivial subset of the functionality that a network such as
Ethereum provides. Examples discussed include: multi-signature wallets in which
funds can be spent by any 2-out-of-3 owners; restricted accounts that can send
funds only to designated destinations; and "colored coins" that can represent
stocks that can be freely traded, and their owner would receive dividends. Our
approach is not as universal as the one used in Ethereum since we do not reach
a consensus regarding the state of a ledger. We call our proposal prudent
contracts to reflect this.
The main building block is either quantum tokens for digital signatures
(Ben-David and Sattath QCrypt'17, Coladangelo et al. Crypto'21), semi-quantum
tokens for digital signatures (Shmueli'22) or one-shot signatures (Amos et al.
STOC'20). The solution has all the benefits of public quantum money: no mining
is necessary, and the security model is standard (e.g., it is not susceptible
to 51\% attacks, as in Bitcoin).
Our one-shot signature construction can be used to upgrade the Bitcoin
network to a quantum payment scheme. Notable advantages of this approach are:
transactions are locally verifiable and without latency, the throughput is
unbounded, and most importantly, it would remove the need for Bitcoin mining.
Our approach requires a universal large-scale quantum computer and long-term
quantum memory; hence we do not expect it to be implementable in the next few
years.Comment: Minor change
Signing Perfect Currency Bonds
We propose the idea of a Quantum Cheque Scheme, a cryptographic protocol in
which any legitimate client of a trusted bank can issue a cheque, that cannot
be counterfeited or altered in anyway, and can be verified by a bank or any of
its branches. We formally define a Quantum Cheque and present the first
Unconditionally Secure Quantum Cheque Scheme and show it to be secure against
any no-signaling adversary. The proposed Quantum Cheque Scheme can been
perceived as the quantum analog of Electronic Data Interchange, as an alternate
for current e-Payment Gateways.Comment: 6 pages, 2 figure
Quotable Signatures for Authenticating Shared Quotes
Quotable signature schemes are digital signature schemes with the additional
property that from the signature for a message, any party can extract
signatures for (allowable) quotes from the message, without knowing the secret
key or interacting with the signer of the original message. Crucially, the
extracted signatures are still signed with the original secret key. We define a
notion of security for quotable signature schemes and construct a concrete
example of a quotable signature scheme, using Merkle trees and classical
digital signature schemes. The scheme is shown to be secure, with respect to
the aforementioned notion of security. Additionally, we prove bounds on the
complexity of the constructed scheme and provide algorithms for signing,
quoting, and verifying. Finally, concrete use cases of quotable signatures are
considered, using them to combat misinformation by bolstering authentic content
on social media. We consider both how quotable signatures can be used, and why
using them could help mitigate the effects of fake news.Comment: 29 pages, 7 figure
IMPROVING SMART GRID SECURITY USING MERKLE TREES
Abstract—Presently nations worldwide are starting to convert their aging electrical power infrastructures into modern, dynamic power grids. Smart Grid offers much in the way of efficiencies and robustness to the electrical power grid, however its heavy reliance on communication networks will leave it more vulnerable to attack than present day grids. This paper looks at the threat to public key cryptography systems from a fully realized quantum computer and how this could impact the Smart Grid. We argue for the use of Merkle Trees in place of public key cryptography for authentication of devices in wireless mesh networks that are used in Smart Grid applications
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