178,186 research outputs found
Multidimensional Zero-Correlation Linear Cryptanalysis of the Block Cipher KASUMI
The block cipher KASUMI is widely used for security in many synchronous
wireless standards. It was proposed by ETSI SAGE for usage in 3GPP (3rd
Generation Partnership Project) ciphering algorthms in 2001. There are a great
deal of cryptanalytic results on KASUMI, however, its security evaluation
against the recent zero-correlation linear attacks is still lacking so far. In
this paper, we select some special input masks to refine the general 5-round
zero-correlation linear approximations combining with some observations on the
functions and then propose the 6-round zero-correlation linear attack on
KASUMI. Moreover, zero-correlation linear attacks on the last 7-round KASUMI
are also introduced under some weak keys conditions. These weak keys take
of the whole key space.
The new zero-correlation linear attack on the 6-round needs about
encryptions with known plaintexts. For the attack under weak keys
conditions on the last 7 round, the data complexity is about known
plaintexts and the time complexity encryptions
Unconditionally secure quantum key distribution over 50km of standard telecom fibre
We demonstrate a weak pulse quantum key distribution system using the BB84
protocol which is secure against all individual attacks, including photon
number splitting. By carefully controlling the weak pulse intensity we
demonstrate the maximum secure bit rate as a function of the fibre length.
Unconditionally secure keys can be formed for standard telecom fibres exceeding
50 km in length.Comment: 9 pages 2 figure
Cryptanalysis of an Image Encryption Scheme Based on a Compound Chaotic Sequence
Recently, an image encryption scheme based on a compound chaotic sequence was
proposed. In this paper, the security of the scheme is studied and the
following problems are found: (1) a differential chosen-plaintext attack can
break the scheme with only three chosen plain-images; (2) there is a number of
weak keys and some equivalent keys for encryption; (3) the scheme is not
sensitive to the changes of plain-images; and (4) the compound chaotic sequence
does not work as a good random number resource.Comment: 11 pages, 2 figure
Removable Weak Keys for Discrete Logarithm Based Cryptography
We describe a novel type of weak cryptographic private key that can exist in
any discrete logarithm based public-key cryptosystem set in a group of prime
order where has small divisors. Unlike the weak private keys based on
\textit{numerical size} (such as smaller private keys, or private keys lying in
an interval) that will \textit{always} exist in any DLP cryptosystems, our type
of weak private keys occurs purely due to parameter choice of , and hence,
can be removed with appropriate value of . Using the theory of implicit
group representations, we present algorithms that can determine whether a key
is weak, and if so, recover the private key from the corresponding public key.
We analyze several elliptic curves proposed in the literature and in various
standards, giving counts of the number of keys that can be broken with
relatively small amounts of computation. Our results show that many of these
curves, including some from standards, have a considerable number of such weak
private keys. We also use our methods to show that none of the 14 outstanding
Certicom Challenge problem instances are weak in our sense, up to a certain
weakness bound
Keys and Armstrong databases in trees with restructuring
The definition of keys, antikeys, Armstrong-instances are extended to complex values in the presence of several constructors. These include tuple, list, set and a union constructor. Nested data structures are built using the various constructors in a tree-like fashion. The union constructor complicates all results and proofs significantly. The reason for this is that it comes along with non-trivial restructuring rules. Also, so-called counter attributes need to be introduced. It is shown that keys can be identified with closed sets of subattributes under a certain closure operator. Minimal keys correspond to closed sets minimal under set-wise containment. The existence of Armstrong databases for given minimal key systems is investigated. A sufficient condition is given and some necessary conditions are also exhibited. Weak keys can be obtained if functional dependency is replaced by weak functional dependency in the definition. It is shown, that this leads to the same concept. Strong keys are defined as principal ideals in the subattribute lattice. Characterization of antikeys for strong keys is given. Some numerical necessary conditions for the existence of Armstrong databases in case of degenerate keys are shown. This leads to the theory of bounded domain attributes. The complexity of the problem is shown through several examples
Experimental demonstration of counterfactual quantum key distribution
Counterfactual quantum key distribution provides natural advantage against
the eavesdropping on the actual signal particles. It can prevent the
photon-number-splitting attack when a weak coherent light source is used for
the practical implementation. We realized the counterfactual quantum key
distribution in an unbalanced Mach-Zehnder interferometer of 12.5-km-long
quantum channel with a high-fringe visibility of 96:4%. As a result, we
obtained secure keys against the noise-induced attack (eg. the vacuum attack)
and passive photon-number-splitting attack.Comment: 5 pages, 3 figure
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