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Lihua Liu

Publications and source records attributed to Lihua Liu.

26 records · Page 2Linked to original sources
arXiv2015

A Note On Boneh-Gentry-Waters Broadcast Encryption Scheme and Its Like

Key establishment is any process whereby a shared secret key becomes available to two or more parties, for subsequent cryptographic use such as symmetric-key encryption. Though it is widely known that the primitive of encryption is different from key establishment, we find some researchers have confused the two primitives. In this note, we shall clarify the fundamental difference between the two primitives, and point out that the Boneh-Gentry-Waters broadcast encryption scheme and its like are key establishment schemes, not encryption schemes.

cs.CR↗
arXiv2014

Remarks on Quantum Modular Exponentiation and Some Experimental Demonstrations of Shor's Algorithm

An efficient quantum modular exponentiation method is indispensible for Shor's factoring algorithm. But we find that all descriptions presented by Shor, Nielsen and Chuang, Markov and Saeedi, et al., are flawed. We also remark that some experimental demonstrations of Shor's algorithm are misleading, because they violate the necessary condition that the selected number $q=2^s$, where $s$ is the number of qubits used in the first register, must satisfy $n^2 \leq q < 2n^2$, where $n$ is the large number to be factored.

cs.DS↗
arXiv2014

The Barth-Boneh-Waters Private Broadcast Encryption Scheme Revisited

The primitive of private broadcast encryption introduced by Barth, Boneh and Waters, is used to encrypt a message to several recipients while hiding the identities of the recipients. In their construction, a recipient has to first decrypt the received ciphertext to extract the verification key for one-time signature. He then uses the verification key to check whether the ciphertext is malformed. The authors did not consider that information delivered over a channel, especially over a broadcast channel, should be authenticated as to its origin. We remark that the conventional public key signature suffices to authenticate data origin and filter out all malformed ciphertexts. We also discuss the disadvantages of the primitive of one-time signature used in their construction.

cs.CR↗
arXiv2014

Remarks on the Cryptographic Primitive of Attribute-based Encryption

Attribute-based encryption (ABE) which allows users to encrypt and decrypt messages based on user attributes is a type of one-to-many encryption. Unlike the conventional one-to-one encryption which has no intention to exclude any partners of the intended receiver from obtaining the plaintext, an ABE system tries to exclude some unintended recipients from obtaining the plaintext whether they are partners of some intended recipients. We remark that this requirement for ABE is very hard to meet. An ABE system cannot truly exclude some unintended recipients from decryption because some users can exchange their decryption keys in order to maximize their own interests. The flaw discounts the importance of the cryptographic primitive.

cs.CR↗
arXiv2014

Remarks on AKS Primality Testing Algorithm and A Flaw in the Definition of P

We remark that the AKS primality testing algorithm [Annals of Mathematics 160 (2), 2004] needs about 1,000,000,000 G (gigabyte) storage space for a number of 1024 bits. The requirement is very hard to meet. The complexity class P which contains all decision problems that can be solved by a deterministic Turing machine using a polynomial amount of computation time, is generally believed to be ``easy". We point out that the time is estimated only in terms of the amount of arithmetic operations. It does not comprise the time for reading and writing data on the tape in a Turing machine. The flaw makes some deterministic polynomial time algorithms impractical, and humbles the importance of P=NP question.

cs.CC↗
arXiv2014

A Fast String Matching Algorithm Based on Lowlight Characters in the Pattern

We put forth a new string matching algorithm which matches the pattern from neither the left nor the right end, instead a special position. Comparing with the Knuth-Morris-Pratt algorithm and the Boyer-Moore algorithm, the new algorithm is more flexible to pick the position for starting comparisons. The option really brings it a saving in cost.

cs.DS↗
arXiv2013

Ordered Probability Mass Function

Suppose that in the four tests Alice's scores are 90, 95, 85, 90, and Bob's scores are 85, 95, 90, 90. How to evaluate their scores? In this paper, we introduce the concept of ordered probability mass function which can be used to find a probability mass function with smaller variance. More interestingly, we can use it to distinguish sequences of positive numbers statistically.

cs.DM↗