13 research outputs found
Signcryption scheme for Identity-based Cryptosystems
An Identity-based cryptosystem is a Public Key cryptosystem in which the public keys of the entities are their identities, or strings derived from their identities. Signcryption combines digital signatures and encryption with a cost significantly smaller than that required for signature-then-encryption. This paper proposes an ID-based signcryption scheme based on bilinear pairings on elliptic curves. It is shown that the new scheme is an improved version of the existing signcryption scheme [10] by comparing the computations in both the schemes
ID-based tripartite Authenticated Key Agreement Protocols from pairings
This paper proposes ID-based tripartite authenticated key agreement protocols. The authenticated three party key agreement protocols from pairings [15], and the ID-based two party authenticated key agreement protocol [13] are studied. These two protocols are taken as the basis for designing three new ID-based tripartite authenticated key agreement protocols. The security properties of all these protocols are studied listing out the possible attacks on them. Further, these protocols are extended to provide key confirmation
ID-Based Tripartite Key Agreement with Signature
This paper proposes a new identity based tripartite key agreement protocol which is more efficient than the existing ID-based tripartite protocol. This protocol is based on the Joux's protocol for key agreement, and introduces signature along with key agreement to overcome man-in-the-middle attacks and to provide authentication. The new protocol resists existential forgeries against adaptively chosen message attacks under the random oracle model
ID-based tripartite key agreement with signatures
This paper proposes a new identity based tripartite key agreement protocol which is more efficient than the existing ID-based tripartite protocol. This protocol is based on the Joux's protocol for key agreement, and introduces signature along with key agreement to overcome man-in-the-middle attacks and to provide authentication. The new protocol resists existential forgeries against adaptively chosen message attacks under the random oracle model
Catalytic Asymmetric Heterodimerization of Ketenes
In this Communication we describe an unprecedented catalytic
asymmetric
heterodimerization of ketenes of wide substrate scope. The alkaloid-catalyzed
method provides access to ketene heterodimer β-lactones and
allows even two different monosubstituted ketenes to be cross-dimerized,
with excellent enantioselectivity (17 examples with ≥90% ee)
and excellent heterodimer regioselectivity observed in all cases
Catalytic Asymmetric Synthesis of Ketene Heterodimer β‑Lactones: Scope and Limitations
In
this article we describe extensive studies of the catalytic asymmetric
heterodimerization of ketenes to give ketene heterodimer β-lactones.
The optimal catalytic system was determined to be a cinchona alkaloid
derivative (TMS-quinine or Me-quinidine). The desired ketene heterodimer
β-lactones were obtained in good to excellent yields (up to
90%), with excellent levels of enantioselectivity (≥90% ee
for 33 <i>Z</i> and <i>E</i> isomer examples),
good to excellent (<i>Z</i>)-olefin isomer selectivity (≥90:10
for 20 examples), and excellent regioselectivity (only one regioisomer
formed). Full details of catalyst development studies, catalyst loading
investigations, substrate scope exploration, protocol innovations
(including double in situ ketene generation for 7 examples), and an
application to a cinnabaramide A intermediate are described. The addition
of lithium perchlorate (1–2 equiv) as an additive to the alkaloid
catalyst system was found to favor formation of the <i>E</i> isomer of the ketene heterodimer. Ten examples were formed with
moderate to excellent (<i>E</i>)-olefin isomer selectivity
(74:25 to 97:3) and with excellent enantioselectivity (84–98%
ee)