Abstract: A method for searchable symmetric encryption. The method includes: accessing a computerized database that comprises keyword lists, each of the keyword lists comprising memory addresses of electronic documents that all contain a respective keyword; binning the memory addresses by performing balanced allocation of the memory addresses into ordered bins, such that at least some of the ordered bins each contains memory addresses of electronic documents that contain different keywords; encrypting each of the memory addresses with an encryption key that is derived from the keyword of the respective memory address; and storing the ordered bins at consecutive locations in a non-transient computer-readable memory, wherein the consecutive locations preserve the order of the ordered bins.

Abstract: A method for searchable symmetric encryption. The method includes: accessing a computerized database that comprises keyword lists, each of the keyword lists comprising memory addresses of electronic documents that all contain a respective keyword; binning the memory addresses by performing balanced allocation of the memory addresses into ordered bins, such that at least some of the ordered bins each contains memory addresses of electronic documents that contain different keywords; encrypting each of the memory addresses with an encryption key that is derived from the keyword of the respective memory address; and storing the ordered bins at consecutive locations in a non-transient computer-readable memory, wherein the consecutive locations preserve the order of the ordered bins.

Abstract: Reducing or deterring undesirable electronic communications by requiring a sender of an electronic communication to download a memory-bound function that describes a table. The function initializes and builds a table, hashes each entry in the table, sorts the table. The steps of hashing and sorting the table may be completed as many times as desired. At the conclusion of the iterations, the table may be hashed a final time to unsort the table. The sender then uses the table in proving a computational function. The proof of the function is sent to a recipient of the electronic communication as proof that the sender has spent computational effort to send the e-mail.

Abstract: A memory containing an authenticated search tree that serves for authenticating membership or non membership of items in a set. The authenticated search tree including a search tree having nodes and leaves and being associated with a search scheme. The nodes including dynamic search values and the leaves including items of the set. The nodes are associated, each, with a cryptographic hash function value that is produced by applying a cryptographic hash function to the cryptographic hash values of the children nodes and to the dynamic search value of the node. The root node of the authenticated search tree is authenticated by a digital signature.

Abstract: A machine-readable check comprising a check and a machine-readable image block printed on the check. Preferably, the image block is a two-dimensional print code.

Abstract: A system and method are provided for producing verified signatures on documents such as checks and affidavits. Initially, a customer who is to obtain a verified signature, at some point in time, registers with a signatory authority, and a secret key, having public and private components, is established uniquely for that customer. When a document requires a verified signature, the customer presents the document and proof of his/her identity, such as a preprogrammed computer-interfacable card, to a signature system. Typically, such a system is to be available at an institution, such as an office, bank, or post office, where such services will routinely be used. The system accesses the archive of the private portion of the customer's key, and generates an encoded signature based, in part, on the content of the document. Accordingly, when a recipient of the document later wishes to verify the signature, the recipient uses the customer's public key to decode the signature.

Abstract: A method for secure accounting and auditing of a communications network operates in an environment in which many servers serve an even larger number of clients (e.g. the web), and are required to meter the interaction between servers and clients (e.g. counting the number of clients that were served by a server). The method (metering process) is very efficient and does not require extensive usage of any new communication channels. The metering is secure against fraud attempts by servers which inflate the number of their clients and against clients that attempt to disrupt the metering process. Several secure and efficient constructions of this method are based on efficient cryptographic techniques, are also very accurate, and preserver the privacy of the clients.

Abstract: A system and method are provided for facilitating proof that a specific item, such as a document, has been sent via a communication medium, such as the mail service of the United States Postal Service, at a specific time. A bit map image is produced, such as by scanning a hard copy document. Preferably the bit map is compressed into a data string and hashed. The hash file is signed by a certifying authority, such as the USPS, using an existentially unforgeable signature scheme. The original document, a code representation of the string, and a code representation of the signature are sent via the communication medium. As a result, the combination of materials sent provides proof of the authenticity of the content of the document.