International Business Machines Corporation

Daniel Kovacs

Jan Leonard Camenisch

Dieter M Sommer

Kai Samelin

Mark Korondi

Zoltan Arnold Nagy

Gregory Neven

Anja Lehmann

Michael Charles Osborne

Methods and systems are provided for demonstrating authorization to access a resource to a verifier computer controlling access to the resource. The method comprises, at a user computer, storing an attribute credential certifying a set of attributes; and communicating with a revocation authority computer to obtain an auxiliary credential, bound to the attribute credential, certifying a validity status for each attribute in the attribute credential. The method further comprises, at the user computer, communicating with the verifier computer to prove possession of the attribute credential and the auxiliary credential such that the verifier computer can determine whether at least one attribute in the attribute credential, certified as valid by the auxiliary credential, satisfies an access condition for the resource.

Credential-based authorization

Methods, systems and computer program products are provided for authenticating a message via a revocable signature. The method includes, at a signing computer, generating first auxiliary data and second auxiliary data respectively dependent on a public key and a private key of a public-private key pair for the message. The signing computer hashes the message and the first auxiliary data via a chameleon hash algorithm, using a public hash key of a verifier computer, to produce a first hash value. The signing computer signs the first hash value, using a secret signing key of the signing computer, to produce a signature. The signing computer sends the message, the signature and the first auxiliary data to the verifier computer, and stores the second auxiliary data.

Authentication via revocable signatures

Methods are provided for authenticating user authentication data, associated with a user ID, at an authentication system. The authentication system comprises an authentication server connected to a network, and a secure cryptoprocessor operatively coupled to the authentication server. A first token for the user ID is provided in data storage operatively coupled to the authentication server. The first token is produced by the secure cryptoprocessor by encoding the user authentication data associated with the user ID via an encoding process dependent on a secret key of the secure cryptoprocessor. The authentication server receives an authentication request for the user ID from a remote computer via the network. The authentication request comprises a ciphertext encrypting user authentication data under a public key of a first public-private key pair, the private key of which is secret to the secure cryptoprocessor. The authentication server supplies the ciphertext to the secure cryptoprocessor which decrypts the ciphertext using this private key to obtain plaintext user authentication data. The authentication server retrieves the first token for the user ID from the data storage. The authentication system checks for equality of the plaintext user authentication data and the user authentication data encoded in the first token via a cryptographic processing operation in which the authentication data is not exposed outside the secure cryptoprocessor. In response to such equality, the authentication server sends an authentication confirmation message to the remote computer via the network.

User authentication over networks

Embodiments include methods for managing encrypted files by storing a user password hash including a predetermined function of the user password associated with that user ID and the secret keys. Aspects also include, in response to receipt from a user computer of an input password and a the user ID for a required encrypted file, communicating with authentication servers to implement a key-reconstruction protocol in which each server computes first and second hash values for the required encrypted file. The file management server uses the first hash values to compute an input password hash including the predetermined function of the input password and the secret keys, checks if the input password hash matches the user password hash for the received user ID, and reconstructs the encryption key for the required encrypted file.

Password-based management of encrypted files

A server system for implementing a distributed cryptographic protocol includes a machine management server which comprises a current virtual machine configured to implement the protocol using a set of communication keys and state information for the protocol. The system further includes a memory and a refresh server. The system is configured, for each of successive new time periods in operation of the protocol, to perform a refresh operation wherein: the refresh server retrieves the state information from the memory, generates a new set of communication keys, and sends the state information and new set of keys to the machine management server; the machine management server configures a new virtual machine for implementing the protocol, whereby the new virtual machine receives the new set of keys and state information sent by the refresh server; and the new virtual machine assumes operation as the current virtual machine for the new time period and stores state information for that time period in the memory.

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Adliswil, Switzerland

Daniel Kovacs