Abstract: Described herein are methods and systems for creating a framework that allows the creation of Secret Interest Groups (SIGs) in Online Social Networks. SIGs are self-managed groups formed outside of the social network, around secret, sensitive, or private topics. A set of cryptographic algorithms are used for the framework implementation.

Abstract: Performing an untraceable secret matching between a first credential associated with a first property of a first user and a second credential associated with a second property of a second user includes receiving the first credential, receiving a matching reference formed so the first user can detect a matching of the first property with a remote property from a credential of another user, supplying a first nonce value to the second user, receiving a hidden version of the second credential from the second user formed by the second user on the basis of the second credential, the first nonce value supplied by the first user and a random value locally generated on a side of the second user, and performing the matching by combining the first credential and the received hidden credential with the first nonce value and comparing the combination with the matching reference.

Abstract: Performing an untraceable secret matching between a first credential associated with a first property of a first user and a second credential associated with a second property of a second user includes receiving the first credential, receiving a matching reference formed so the first user can detect a matching of the first property with a remote property from a credential of another user, supplying a first nonce value to the second user, receiving a hidden version of the second credential from the second user formed by the second user on the basis of the second credential, the first nonce value supplied by the first user and a random value locally generated on a side of the second user, and performing the matching by combining the first credential and the received hidden credential with the first nonce value and comparing the combination with the matching reference.

Abstract: A robust and secure password (or key) change method between a user and an authentication server in a distributed communication network is disclosed. The protocol requires the exchange of only two messages between the user desiring the key change and the server, the user's request including, at least partly encrypted, an identification of the sending user, old and new keys, and two nonces, at least one including a time indication. The authentication server's response includes a possibly encrypted accept/reject indication and the regularly encrypted request from the user.

Abstract: This invention relates to a novel smartcard-based authentication technique using a smartcard that encrypts the time displayed on the card with a secret, cryptographically strong key. The (public) work station receives as input certain values defining the user, the card and a particular value derived from the encrypted time and encrypts and/or transmits these values to the server. The server, in turn, computes from received values some potential values and compares these to other received values. If the server determines a match, an accept signal is transmitted to the work station.