Abstract: A method for providing a proof-of-work includes computing, by a verification computing device (VCD), a first linear feedback shift register sequence (LFSR-S) using a first polynomial having a first degree and computing, by the VCD, a second LFSR-S based on a second polynomial. A challenge, generated by the VCD and using elements of the second LFSR-S, is transmitted to the PCD. The PCD recursively computes all elements of the first LFSR-S by using the elements and coefficients of the second LFSR-S. A solution for the received challenge is computed based on the computed elements of the first LFSR-S. A proof-of-work is provided by verifying, by the VCD, the transmitted solution by: recomputing a solution to the challenge using initial state parameters and coefficients of the first LFSR-S, and comparing the computed solution of the PCD with the recomputed solution of the VCD.

Abstract: A method for storing data in a cloud includes providing at least one data file to be stored together with a predefined number t of replicas of the at least one data file within the cloud, at least one authentication tag corresponding to the at least one data file and t functions that are configurable to take at least a predefined time to compute. The at least one data file, the at least one authentication tag and the t functions are transmitted to the cloud. The at least one data file is stored within the cloud and t solutions of the t functions are computed within the cloud. The t replicas of the at least one data file are generated based on the t solutions of the t functions and the at least one data file within the cloud. The t replicas are stored within the cloud.

Abstract: A method for storing a data file of a client on a storage entity includes generating, by a proxy entity, a master encryption key; encrypting, by the client, the data file using the master encryption key to produce an encrypted file; computing a hash-tree for the encrypted file and using a top-hash of the hash-tree as a file identification (FID); and determining, by the proxy entity, whether the HD is already known to the storage entity. If the FID is not already known to the storage entity the method further includes computing, by the proxy entity, a top-hash of the encrypted file (PFID), and when the ownership of the data file has been proven, storing the FID being equal with the PFID at the client together with the hash value.

Abstract: A method for verifying information of a first data item in a plurality of different data items stored on a server includes a) generating a hash tree, b) computing an authentication path for the first data item based on a recomputation of the hash tree, wherein an authentication path comprises all siblings of tree nodes from the first data item to a root of the hash tree, e) recomputing the root-latish based on the first data item and a computed authentication path of the first data item and comparing the recomputed root-hash with the root-hash of the hash-tree of step a), d) determining a side element in leaves or a tree level above of the hash tree and its authentication path, and e) verifying the authentication path of the side dement.

Abstract: A method for proving retrievability (POR) of information is performed in a memory available to one or more computation devices, wherein credentials between a user device, a storing device and an auditing device between each pair of said devices are exchanged and used for communication between them. The method includes encoding information to be stored on the storing device by the user device or the auditing device, storing the encoded information on the storing device, verifying the correctness of the stored information by the auditing device using unpredictable random information, transmitting correctness information to the user device, the correctness information being secure and being generated based on the result of the verification by the auditing device, and validating the correctness information by the user device for proving retrievability of the stored information and the unpredictable random information.

Abstract: A key exchanging apparatus transmits the contribution data to the plurality of counterpart apparatuses, generates a signer contribution confirmation signature with respect to a contribution data set including all the contribution data received from the plurality of counterpart apparatuses, generates auxiliary data and auxiliary data validity certification sentence from the contribution data set and the contribution random number, transmits the auxiliary data, the auxiliary data validity certification sentence and the contribution confirmation signature to the plurality of counterpart apparatuses, verifies validity of auxiliary data by using the counterpart identifier set, the counterpart public key set, the contribution confirmation signature set including the data received from the plurality of counterpart apparatuses, the auxiliary data set and the auxiliary data validity certification sentence set, and generates a public key from the contribution data set and the auxiliary data received from the plurality

Abstract: A method for establishing a secret key between two nodes in a communication network, in particular in a wireless local area network (WLAN), includes concealment of the fact that a key exchange occurs, one of the nodes—first node (B)—broadcasts one or more packets (Pi) that can be received by the other node—second node (A)—, wherein the packets (Pi) contain each a first key (Ki) and wherein the packets (Pi) are each encrypted with a second key (ki) before being sent, the second node (A) randomly chooses one packet (Pm) from the packets (Pi) received and breaks the encryption of the chosen packet (Pm) in order to obtain the first key (Km), and the second node (A) initiates a key exchange protocol, wherein the second node (A) encrypts the message to be sent for initiating the key exchange protocol with the revealed key (Km).

Abstract: A method for aggregating data in a network, particularly in a wireless sensor network, wherein the network (1) includes a plurality of sensor nodes (Ni) to measure data and at least one sink node (S) at which the data measured by the sensor nodes (Ni) are aggregated, and wherein each sensor node (Ni) encrypts its measured data with a key k and forwards the result towards the sink node (S), is characterized in that, in the context of a key distribution within the network (1), a master key K is chosen, and that the master key K is autonomously split up by the network (1) into individual keys ki to be used by the sensor nodes (Ni) for encrypting measured data, with the sum of all individual keys ki being equal to the master key K.

Abstract: A method for electing aggregator nodes in a network, wherein the network includes a plurality of sensor nodes to measure data, and at least one of the sensor nodes functioning as aggregator node to aggregate sensored data obtained by at least a subset of the sensor nodes, the network further including at least one sink node to collect data aggregated by the aggregator nodes, the method including: establishing pairwise secret keys between a current aggregator node and each sensor node of the subset of sensor nodes; at each of the sensor nodes of the subset, choosing a random number and encrypting the random number using the established key; providing a communication chain between the sensor nodes of the subset and summing the encrypted random numbers of all sensor nodes of the subset; and determining a new aggregator node on the basis of the resulting sum according to a predefined calculation scheme.

Abstract: A key exchanging apparatus transmits the contribution data to the plurality of counterpart apparatuses, generates a signer contribution confirmation signature with respect to a contribution data set including all the contribution data received from the plurality of counterpart apparatuses, generates auxiliary data and auxiliary data validity certification sentence from the contribution data set and the contribution random number, transmits the auxiliary data, the auxiliary data validity certification sentence and the contribution confirmation signature to the plurality of counterpart apparatuses, verifies validity of auxiliary data by using the counterpart identifier set, the counterpart public key set, the contribution confirmation signature set including the data received from the plurality of counterpart apparatuses, the auxiliary data set and the auxiliary data validity certification sentence set, and generates a public key from the contribution data set and the auxiliary data received from the plurality

Abstract: A method for aggregating data in a network, particularly in a wireless sensor network, wherein the network (1) includes a plurality of sensor nodes (Ni) to measure data and at least one sink node (S) at which the data measured by the sensor nodes (Ni) are aggregated, and wherein each sensor node (Ni) encrypts its measured data with a key k and forwards the result towards the sink node (S), is characterized in that, in the context of a key distribution within the network (1), a master key K is chosen, and that the master key K is autonomously split up by the network (1) into individual keys ki to be used by the sensor nodes (Ni) for encrypting measured data, with the sum of all individual keys ki being equal to the master key K.

Abstract: A method for electing aggregator nodes in a network, wherein the network includes a plurality of sensor nodes to measure data, and at least one of the sensor nodes functioning as aggregator node to aggregate sensored data obtained by at least a subset of the sensor nodes, the network further including at least one sink node to collect data aggregated by the aggregator nodes, the method including: establishing pairwise secret keys between a current aggregator node and each sensor node of the subset of sensor nodes; at each of the sensor nodes of the subset, choosing a random number and encrypting the random number using the established key; providing a communication chain between the sensor nodes of the subset and summing the encrypted random numbers of all sensor nodes of the subset; and determining a new aggregator node on the basis of the resulting sum according to a predefined calculation scheme.

Abstract: A method for establishing a secret key between two nodes in a communication network, in particular in a wireless local area network (WLAN), includes concealment of the fact that a key exchange occurs, one of the nodes—first node (B)—broadcasts one or more packets (Pi) that can be received by the other node—second node (A)—, wherein the packets (Pi) contain each a first key (Ki) and wherein the packets (Pi) are each encrypted with a second key (ki) before being sent, the second node (A) randomly chooses one packet (Pm) from the packets (Pi) received and breaks the encryption of the chosen packet (Pm) in order to obtain the first key (Km), and the second node (A) initiates a key exchange protocol, wherein the second node (A) encrypts the message to be sent for initiating the key exchange protocol with the revealed key (Km).