摘要:
A first processing device, which may be, for example, a wireless authentication token or an RFID tag, comprises a memory, a processor coupled to the memory, and interface circuitry coupled to the processor. The processor is operative to control the output of authentication information via the interface circuitry, where the authentication information comprises a sequence of values corresponding to images of a hash chain. A given one of the values of the sequence is utilized by a second processing device to generate a modified value suitable for providing joint authentication of the first and second processing devices.
摘要:
This invention relates to cryptographic communications methods and systems that protect a server from a connection depletion attack. Specifically, the invention presents a method for allocating a resource comprising the steps of receiving a resource allocation request from a client, imposing a computational task and a time limit for correct completion of the task upon the client, verifying that the task was performed correctly within the time limit, and allocating the resource if the task was correctly performed within the time limit.
摘要:
A highly efficient mix network for small numbers of inputs is provided. Four data messages would be a typical number of inputs. The structure of sorting/permutation networks is used to permute the input. This is done in a way that changes the position of pairs of items. A mix network is provided which is highly efficient on small input batches and is robust and private in the face of collusion by any minority set of mix servers. Additionally, the mix network method and apparatus has the feature of being publicly verifiable because the mixing method yields a transcript of results that can demonstrate to a third party that the mix proceeded correctly. An apparatus comprised of a plurality of mix servers is provided. Each mix server includes a randomizer network. Each randomizer network receives a plurality of input data messages and performs re-encryption and permutation operations on the plurality of input data messages to form a plurality of output data messages. The randomizer networks of the plurality of mix servers are arranged in a chain so that the first randomizer network of the first mix server in the chain receives its plurality of input data messages and provides its plurality of output data messages to the next randomizer network of the following mix server in the chain. Each randomizer network is comprised of a plurality of randomizers, wherein each randomizer receives first and second input data messages and produces first and second output data messages, wherein the first output data message is a re-encryption of either the first or the second input data message and the second output data message is a re-encryption of the other input data message. A bulletin board having computer memory may be provided, to which each mix server produces proof that each randomizer of each randomizer network has re-encrypted and permuted in a proper manner.
摘要:
Methods and apparatus are disclosed for demonstrating that a public/private key pair is cryptographically strong without revealing information sufficient to compromise the private key. A key pair can be shown to be cryptographically strong by demonstrating that its modulus N is the product of two relatively large prime numbers. In addition, a key pair can be shown to be cryptographically strong by demonstrating that N is cryptographically strong against Pollard factoring attacks, Williams factoring attacks, Bach-Shallit factoring attacks, and weighted difference of squares factoring attacks.
摘要:
The invention provides techniques for implementing secure transactions using an instrument referred to as "executable digital cash." In an illustrative embodiment, a first user generates a piece of digital cash representing an offer made by that user. The piece of digital cash includes a digital certificate authorizing the first user to make specified transfers, and an offer program characterizing the offer. The piece of digital cash is broadcast or otherwise transmitted to one or more additional users, utilizing a mobile agent or other suitable mechanism, such that a given one of these users can evaluate the offer using the offer program. For example, a second user could execute the offer program with a specific bid as an input to determine what that user would receive upon acceptance of his bid. If the result is acceptable to the second user, that user generates a bid capsule including the bid, the corresponding output of the offer program, and another certificate authorizing the second user to make the transfer specified in the bid. The bid capsule is submitted to an institution for processing in accordance with a policy which may be specified in the piece of digital cash. The institution selects one or more winning bids and implements the corresponding transactions. Digital signatures generated using secret keys associated with the certificates of the first and second users are utilized to ensure adequate security for the transmitted offer and bid information.