Abstract: A password authentication system includes an access control server configured to control access by a user computer to a resource dependent on authentication of user passwords associated with user IDs. The system further includes a plurality of authentication servers, storing respective secret values. For each user ID, the access control server stores a first ciphertext produced by encrypting the user password associated with that ID using a predetermined algorithm dependent on the secret values. In response to receipt of a user ID and an input password, the access control server communicates with the plurality of authentication servers to implement password authentication, requiring use of the secret values, in which a second ciphertext is produced by encrypting the input password using said predetermined algorithm. The access control server compares the first and second ciphertexts to determine whether the input password equals the user password to permit access to the resource.

Abstract: A password authentication system includes an access control server configured to control access by a user computer to a resource dependent on authentication of user passwords associated with user IDs. The system further includes a plurality of authentication servers, storing respective secret values. For each user ID, the access control server stores a first ciphertext produced by encrypting the user password associated with that ID using a predetermined algorithm dependent on the secret values. In response to receipt of a user ID and an input password, the access control server communicates with the plurality of authentication servers to implement password authentication, requiring use of the secret values, in which a second ciphertext is produced by encrypting the input password using said predetermined algorithm. The access control server compares the first and second ciphertexts to determine whether the input password equals the user password to permit access to the resource.

Abstract: A method and system configured to produce a cryptographic signature on a message, under a key, at a user computer wherein the key is shared between the user computer, which stores a first key-share, and an authentication computer, which stores a second key-share and a first authentication value. The user computer encodes the message to produce a blinded message, produces the first authentication value from a user password and a secret value, and produces a second authentication value by encoding the first authentication value and a nonce. The authentication computer uses the nonce to determine if the first authentication value is correct and, if so, encodes the blinded message using the second key-share to produce a partial signature. The user computer produces a signature on the message under the key by encoding the partial signature and the message using the first key-share and an unblinding function.

Abstract: A method and system configured to produce a cryptographic signature on a message, under a key, at a user computer wherein the key is shared between the user computer, which stores a first key-share, and an authentication computer, which stores a second key-share and a first authentication value. The user computer encodes the message to produce a blinded message, produces the first authentication value from a user password and a secret value, and produces a second authentication value by encoding the first authentication value and a nonce. The authentication computer uses the nonce to determine if the first authentication value is correct and, if so, encodes the blinded message using the second key-share to produce a partial signature. The user computer produces a signature on the message under the key by encoding the partial signature and the message using the first key-share and an unblinding function.

Abstract: Effecting reissue in a data processing system of a cryptographic credential certifying a set of attributes, the credential being initially bound to a first secret key stored in a first processing device. A backup token is produced using the first device and comprises a commitment to said set of attributes and first proof data permitting verification that the set of attributes in said commitment corresponds to the set of attributes certified by said credential. At a second processing device, a second secret key is stored and blinded to produce a blinded key. A credential template token produced from the backup token and the blinded key is sent to a credential issuer where said verification is performed using the first proof data and the credential template token is used to provide a reissued credential, certifying said set of attributes, to the second device, the reissued credential being bound to the second secret key.

Abstract: A method, apparatus, and a computer readable storage medium having computer readable instructions to carry out the steps of the method for anonymous access to a database. Each record of the database has different access control permissions (e.g. attributes, roles, or rights). The method allows users to access the database record while the database does not learn who queries a record. The database does not know which record is being queried: (i) the access control list of that record or (ii) whether a user's attempt to access a record had been successful. The user can only obtain a single record per query and only those records for which he has the correct permissions. The user does not learn any other information about the database structure and the access control lists other than whether he was granted access to the queried record, and if so, the content of the record.

Abstract: A method for deriving a verification token from a credential may be provided. The credential may be a set of attributes certified by an issuer to a user using a public key of the issuer. The method may comprise generating the verification token out of the credential and binding the verification token to a context string, wherein the verification token may comprise at least one commitment. A commitment may be a blinded version of an attribute. The method may also comprise generating an opening key for the verification token enabling a generation of a confirmation for a validity of the attribute.

Abstract: A method, apparatus, and a computer readable storage medium having computer readable instructions to carry out the steps of the method for anonymous access to a database. Each record of the database has different access control permissions (e.g. attributes, roles, or rights). The method allows users to access the database record while the database does not learn who queries a record. The database does not know which record is being queried: (i) the access control list of that record or (ii) whether a user's attempt to access a record had been successful. The user can only obtain a single record per query and only those records for which he has the correct permissions. The user does not learn any other information about the database structure and the access control lists other than whether he was granted access to the queried record, and if so, the content of the record.

Abstract: A method, apparatus, and a computer readable storage medium having computer readable instructions to carry out the steps of the method for anonymous access to a database. Each record of the database has different access control permissions (e.g. attributes, roles, or rights). The method allows users to access the database record while the database does not learn who queries a record. The database does not know which record is being queried: (i) the access control list of that record or (ii) whether a user's attempt to access a record had been successful. The user can only obtain a single record per query and only those records for which he has the correct permissions. The user does not learn any other information about the database structure and the access control lists other than whether he was granted access to the queried record, and if so, the content of the record.

Abstract: A protocol for anonymous access to a database where the different records have different access control permissions is described. The permissions can be attributes, roles or rights that an authorized user needs to have to access the record. The database provider does not learn which record the user accesses and which attributes or roles the user has when she accesses the database. The database provider publishes the encrypted database where each record is encrypted with a key that is derived from at least the index of the record, its access control attributes and a secret key of the database provider. The user obtains a credential from an issuer for each access control attribute (ACL) that is associated with the user. Then the user retrieves the key for a particular record from the database provider and uses this key to decrypt the encrypted record.

Abstract: A protocol that allows customers to buy database records while remaining fully anonymous, i.e. the database server does not learn who purchases a record, and cannot link purchases by the same customer; the database server does not learn which record is being purchased, nor the price of the record that is being purchased; the customer can only obtain a single record per purchase, and cannot spend more than his account balance; the database server does not learn the customer's remaining balance. In the protocol customers keep track of their own balances, rather than leaving this to the database server. The protocol allows customers to anonymously recharge their balances.

Abstract: A method, apparatus, and a computer readable storage medium having computer readable instructions to carry out the steps of the method for anonymous access to a database. Each record of the database has different access control permissions (e.g. attributes, roles, or rights). The method allows users to access the database record while the database does not learn who queries a record. The database does not know which record is being queried: (i) the access control list of that record or (ii) whether a user's attempt to access a record had been successful. The user can only obtain a single record per query and only those records for which he has the correct permissions. The user does not learn any other information about the database structure and the access control lists other than whether he was granted access to the queried record, and if so, the content of the record.

Abstract: A protocol for anonymous access to a database where the different records have different access control permissions is described. The permissions can be attributes, roles or rights that an authorized user needs to have to access the record. The database provider does not learn which record the user accesses and which attributes or roles the user has when she accesses the database. The database provider publishes the encrypted database where each record is encrypted with a key that is derived from at least the index of the record, its access control attributes and a secret key of the database provider. The user obtains a credential from an issuer for each access control attribute (ACL) that is associated with the user. Then the user retrieves the key for a particular record from the database provider and uses this key to decrypt the encrypted record.