(Strong) Multi-Designated Verifiers Signatures Secure against Rogue Key Attack

Designated verifier signatures (DVS) allow a signer to create a signature whose validity can only be verified by a specific entity chosen by the signer. In addition, the chosen entity, known as the designated verifier, cannot convince any body that the signature is created by the signer. Multi-designated verifiers signatures (MDVS) are a natural extension of DVS in which the signer can choose multiple designated verifiers. DVS and MDVS are useful primitives in electronic voting and contract signing. In this paper, we investigate various aspects of MDVS and make two contributions. Firstly, we revisit the notion of unforgeability under rogue key attack on MDVS. In this attack scenario, a malicious designated verifier tries to forge a signature that passes through the verification of another honest designated verifier. A common counter-measure involves making the knowledge of secret key assumption (KOSK) in which an adversary is required to produce a proof-of-knowledge of the secret key. We strengthened the existing security model to capture this attack and propose a new construction that does not rely on the KOSK assumption. Secondly, we propose a generic construction of strong MDVS

Asymmetric Message Franking: Content Moderation for Metadata-Private End-to-End Encryption

Content moderation is crucial for stopping abuse and harassment via messaging on online platforms. Existing moderation mechanisms, such as message franking, require platform providers to see user identifiers on encrypted traffic. These mechanisms cannot be used in messaging systems in which users can hide their identities, such as Signal. The key technical challenge preventing moderation is in simultaneously achieving cryptographic accountability while preserving deniability. In this work, we resolve this tension with a new cryptographic primitive: asymmetric message franking schemes (AMFs). We define strong security notions for AMFs, including the first formal treatment of deniability in moderation settings. We then construct, analyze, and implement an AMF scheme that is fast enough for deployment. We detail how to use AMFs to build content moderation for metadata-private messaging

On Classifying Conference Key Distribution Protocols

In this paper, we examine a classification of conference key distribution protocols proposed in [4] and show that no known protocol satisfies the security requirements in class 4, the highest security class of this classification. We show two new attacks on protocols that were believed to belong to the highest security class and show that both protocols in fact belong to class 3. This motivates us to propose a refinement of this classification to allow separating protocols with different security properties while maintaining the classification framework.SCOPUS: cp.kinfo:eu-repo/semantics/publishe

Lipid peroxidation following superior mesenteric artery occlusion in rat intestine

Background: The aim of this study was to determine the level of lipid peroxidation and tissue protein after superior mesenteric artery occlusion tissue damage. The effect of melatonin as anti oxidant and free radical scavenger in prevention of tissue damage, were also evaluated. Methods: Thity six young male Wisatr-Albino rats (weight: 80-120 gr), were divided equally in 6 group with different concentrations of melatonin (10,20,30 mg/kg) treatment. Group 1was control, group 2 the sham that surgical process was applied until superior mesenteric artery dissection and received vehicle solution only in equally volume by intra muscular route. Group 3 was ischemia- reperfusion (I/R), group 4 was I/R plus melatonin 10 mg/kg, group 5 I/R plus melatonin 20 mg/kg and finally group 6 I/R plus melatonin 30 mg/kg. After laparatomy, a microvascular atraumatic clip was placed across the superior mesenteric artery under general anaesthesia and itbremoved after ischemia for 30 minutes. The first dose of melatonin was applied just beforereperfusion, second dose, after reperfusion and third dose on the second day .On third day rats were killed and their bowels were removed. The level of tissue melandialdehyde (MDA) as index of lipid peroxidation and tissue protein was determined. Results: The level of tissue MDA were significantly lower in group 4, 5, 6 than group 3 (p0, 05). Conclusion: These results suggest that melatonin 10 mg/kg has antioxidant effect in prevention of inducing tissue damage during SMA occlusion in rat intestine

Differentiation of human dental pulp stem cells into functional motor neuron: In vitro and ex vivo study

There are several therapeutic options for spinal cord injury (SCI), among these strategies stem cell therapy is a potential treatment. The stem cells based therapies have been investigating in acute phase of clinical trials for promoting spinal repair in humans through replacement of functional neuronal and glial cells. The aim of this study was to evaluate the differentiation of Human Dental Pulp Stem Cells (hDPSCs) into functional motor neuron like cells (MNLCs) and promote neuroregeneration by stimulating local neurogenesis in the adult spinal cord slice culture. The immunocytochemistry analysis demonstrated that hDPSCs were positive for mesenchymal stem cell markers (CD73, CD90 and CD105) and negative for the hematopoietic markers (CD34 and CD45). hDPSCs were induced to neurospheres (via implementing B27, EGF, and bFGF) and then neural stem cells (NSC). The NSC differentiated into MNLCs in two steps: first by Shh and RA and; then with GDNF and BDNF administration. The NS and the NSC were assessed for Oct4, nestin, Nanog, Sox2 expression while the MNLCs were evaluated by ISLET1, Olig2, and HB9 genes. Our results showed that hDPSC can be differentiated into motor neuron phenotype with expression of the motor neuron genes. The functionality of MNLCs was demonstrated by FM1-43, intracellular calcium ion shift and co- culture with C2C12. We co-cultivated hDPSCs with adult rat spinal slices in vitro. Immunostaining and hoechst assay showed that hDPSCs were able to migrate, proliferate and integrate in both the anterolateral zone and the edges of the spinal slice