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Digital Signature Schemes
Published in Jonathan Katz, Yehuda Lindell, Introduction to Modern Cryptography, 2020
The web of trust model is attractive because it does not require trust in any central authority. On the other hand, while it may work well for the average user encrypting their email, it does not seem appropriate for settings where security is more critical, or for the distribution of organizational public keys (e.g., for e-commerce on the web). If a user wants to communicate with his bank, for example, it is unlikely that he would trust people he met at a conference to certify his bank’s public key, and also unlikely that a bank representative will go to a key-signing party to get the bank’s key certified.
Trust and Distrust based Cross-domain Recommender System
Published in Applied Artificial Intelligence, 2021
Collaborative filtering (CF) is a method whose basis is “word-of-mouth” where people recommend various items to others. The basis of CF is previous ratings which can be collected in explicit and/or implicit way. The explicit way of computation uses feedback provided by users, e.g., ratings, and the implicit way involves the analysis of user’s behavior while using the internet. Trust can be incorporated either by user’s explicit involvement, i.e., by specifying their personalized web-of-trust or to build some trust model by involving users direct or indirect feedback. Involving user’s feedback directly into the trust computation has a drawback of additional effort by user which results into cold start problem. So the effective way of trust computation is on the basis of items and user profile. The propagation of trust is the combination of direct and indirect trust (Guha et al. 2004). A direct trust is the factor for which a user has expressed or the computation provides trust value for other users. Indirect trust involves with the propagation of trust where direct trusted neighbors propagate their trust score to other users in the process. Also, a user can't remain trustworthy as time passes i.e. after some time trust formation process should be repeated. Trust propagation can be understood as: suppose a user ‘i’ trust user ‘j’ and user ‘j’ trust user ‘k’. So by applying transitive operation on the trust propagation strategy this can be concluded that user ‘i’ might trust user ‘k’. The same trust propagation can be applied to other case in the related area by using some other operation. Incorporation of trust in the recommendation process solves several issues of recommendation. But now the question arises that whether all users are trustworthy and all of them are allowed to get involved in the propagation network. The problem has been discussed by several researchers which results into another important factor of recommendation “distrust”.