Abstract: One of n?2 servers, connectable via a network, implements a cryptographic protocol using a secret key K which is shared between the n servers, and includes first and second server compartments. The first is connectable to the network, adapted to implement the cryptographic protocol, and stores a current key share of the secret key K. The second is inaccessible from the network in the operation of the server, stores a set of master keys, and is adapted, for each of successive time periods, to unilaterally generate a new key share of the secret key K and to supply it to the first as the current key share for that time period. The new key share includes a random share of a predetermined value p which is shared between the n servers, and the random share includes a function of the set of master keys.

Abstract: Respective cryptographic shares of password data, dependent on a user password, are provided at n authentication servers. A number t1?n of the password data shares determine if the user password matches a password attempt. Respective cryptographic shares of secret data, enabling determination of a username for each verifier server, are provided at n authentication servers. A number t2?t1 of the shares reconstruct the secret data. For a password attempt, the user computer communicates with at least t1 authentication servers to determine if the user password matches the password attempt and, if so, the user computer receives at least t2 secret data shares from respective authentication servers. The user computer uses the secret data to generate, with T?t1 of said t1 servers, a cryptographic token for authenticating the user computer to a selected verifier server, secret from said at least T servers, under said username.

Abstract: Respective cryptographic shares of password data, dependent on a user password, are provided at n authentication servers. A number t1?n of the password data shares determine if the user password matches a password attempt. Respective cryptographic shares of secret data, enabling determination of a username for each verifier server, are provided at n authentication servers. A number t2?t1 of the shares reconstruct the secret data. For a password attempt, the user computer communicates with at least t1 authentication servers to determine if the user password matches the password attempt and, if so, the user computer receives at least t2 secret data shares from respective authentication servers. The user computer uses the secret data to generate, with T?t1 of said t1 servers, a cryptographic token for authenticating the user computer to a selected verifier server, secret from said at least T servers, under said username.

Abstract: Respective cryptographic shares of password data, dependent on a user password, are provided at n authentication servers. A number t1?n of the password data shares determine if the user password matches a password attempt. Respective cryptographic shares of secret data, enabling determination of a username for each verifier server, are provided at n authentication servers. A number t2?t1 of the shares reconstruct the secret data. For a password attempt, the user computer communicates with at least t1 authentication servers to determine if the user password matches the password attempt and, if so, the user computer receives at least t2 secret data shares from respective authentication servers. The user computer uses the secret data to generate, with T?t1 of said t1 servers, a cryptographic token for authenticating the user computer to a selected verifier server, secret from said at least T servers, under said username.

Abstract: A method, computer program product, and system for providing verification processes associated with a commitment-based authentication protocol are described. A request by a user for access to one or more resources is received, and a presentation policy is transmitted to the user indicating required credentials. A commitment to a revocation handle is received, including an indication of an associated Sigma protocol executed by the user. A challenge value selected from a challenge value set associated with the associated Sigma protocol is transmitted to the user. Based on the selected challenge value, a presentation token and a value parameter that is distinct from the presentation token are received from the user. Based on a determination as to whether the presentation token and value parameter are valid in accordance with the associated Sigma protocol, access for the user to the one or more resources is granted to the user or prevented.

Abstract: Systems and methods are provided for proving plaintext knowledge of a message m, encrypted in a ciphertext, to a verifier computer. The method includes, at a user computer, encrypting the message m via a predetermined encryption scheme to produce a ciphertext u, and generating a plurality l of challenges ci, i=1 to l, dependent on the ciphertext u. For each challenge ci, the user computer generates a cryptographic proof ?2i comprising that challenge ci and a zero-knowledge proof of plaintext knowledge of the message m encrypted in the ciphertext u. The user computer sends the ciphertext u and the l proofs ?2i to the verifier computer. Each challenge ci is constrained to a predetermined challenge space C permitting identification, by searching the challenge space C, of an element ci? such that the message m can be obtained via a decryption operation using the ciphertext u, the element ci?, and a decryption key of said encryption scheme.

Abstract: Embodiments of the present invention may provide the capability for performing public-key encryption with proofs of plaintext knowledge using a lattice-based scheme that provides improved efficiency over conventional techniques. For example, in an embodiment, a computer-implemented method of verifying encryption may comprise generating a ciphertext, derived from a plaintext, via an encryption scheme, proving validity of the ciphertext, wherein the proof includes at least one challenge value, and using a decryption procedure that recovers a plaintext by choosing at least one additional challenge value at random from a challenge space.

Abstract: Respective cryptographic shares of password data, dependent on a user password, are provided at n authentication servers. A number t1?n of the password data shares determine if the user password matches a password attempt. Respective cryptographic shares of secret data, enabling determination of a username for each verifier server, are provided at n authentication servers. A number t2?t1 of the shares reconstruct the secret data. For a password attempt, the user computer communicates with at least t1 authentication servers to determine if the user password matches the password attempt and, if so, the user computer receives at least t2 secret data shares from respective authentication servers. The user computer uses the secret data to generate, with T?t1 of said t1 servers, a cryptographic token for authenticating the user computer to a selected verifier server, secret from said at least T servers, under said username.

Abstract: A method, computer program product, and system for providing verification processes associated with a commitment-based authentication protocol are described. A request by a user for access to one or more resources is received, and a presentation policy is transmitted to the user indicating required credentials. A commitment to a revocation handle is received, including an indication of an associated Sigma protocol executed by the user. A challenge value selected from a challenge value set associated with the associated Sigma protocol is transmitted to the user. Based on the selected challenge value, a presentation token and a value parameter that is distinct from the presentation token are received from the user. Based on a determination as to whether the presentation token and value parameter are valid in accordance with the associated Sigma protocol, access for the user to the one or more resources is granted to the user or prevented.

Abstract: Respective cryptographic shares of password data, dependent on a user password, are provided at n authentication servers. A number t1?n of the password data shares determine if the user password matches a password attempt. Respective cryptographic shares of secret data, enabling determination of a username for each verifier server, are provided at n authentication servers. A number t2?t1 of the shares reconstruct the secret data. For a password attempt, the user computer communicates with at least t1 authentication servers to determine if the user password matches the password attempt and, if so, the user computer receives at least t2 secret data shares from respective authentication servers. The user computer uses the secret data to generate, with T?t1 of said t1 servers, a cryptographic token for authenticating the user computer to a selected verifier server, secret from said at least T servers, under said username.

Abstract: Respective cryptographic shares of password data, dependent on a user password, are provided at n authentication servers. A number t1?n of the password data shares determine if the user password matches a password attempt. Respective cryptographic shares of secret data, enabling determination of a username for each verifier server, are provided at n authentication servers. A number t2?t1 of the shares reconstruct the secret data. For a password attempt, the user computer communicates with at least t1 authentication servers to determine if the user password matches the password attempt and, if so, the user computer receives at least t2 secret data shares from respective authentication servers. The user computer uses the secret data to generate, with T?t1 of said t1 servers, a cryptographic token for authenticating the user computer to a selected verifier server, secret from said at least T servers, under said username.

Abstract: Authentication of a device through a constructed authentication token. Components of an authentication key are distributed across at least a device and a server, diminishing a likelihood that an individual account is compromised by an attack.

Abstract: The invention relates to an obfuscated program logic of machine executable instructions and a hardcoded cryptographic signing key. The obfuscated program logic further comprising a hardcoded first attribute value wherein execution of the machine executable instructions by the processor causes the obfuscated program logic to receive a request and in response to receiving the request evaluate whether the request is related to the hardcoded first attribute value. In case the request is related to the hardcoded first attribute value, then computing with the hardcoded first attribute value a response to the request and computing with the cryptographic signing key a signature, wherein the signature certifies the request for which the response was computed and certifies the authenticity of the response. Then generating and returning a presentation token comprising the response and the signature, and providing the presentation token to a receiver computer system.

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 user computer generates a secret cryptographic key through communication with a server. A secret user value is provided at the user computer. A secret server value is provided at the server with a check value which encodes the secret user value and a user password. In response to input of an input password, the user computer encodes the secret user value and the input password to produce a first value corresponding to said check value, and communicates the first value to the server. The server compares the first value and check value to check whether the input password equals the user password. If so, the server encodes the first value and secret server value to produce a second value and communicates the second value to the user computer. The user computer generates the secret cryptographic key by encoding the second value, the input password and the secret user value.

Abstract: One of n?2 servers, connectable via a network, implements a cryptographic protocol using a secret key K which is shared between the n servers, and includes first and second server compartments. The first is connectable to the network, adapted to implement the cryptographic protocol, and stores a current key share of the secret key K. The second is inaccessible from the network in the operation of the server, stores a set of master keys, and is adapted, for each of successive time periods, to unilaterally generate a new key share of the secret key K and to supply it to the first as the current key share for that time period. The new key share includes a random share of a predetermined value p which is shared between the n servers, and the random share includes a function of the set of master keys.

Abstract: Respective cryptographic shares of password data, dependent on a user password, are provided at n authentication servers. A number t1?n of the password data shares determine if the user password matches a password attempt. Respective cryptographic shares of secret data, enabling determination of a username for each verifier server, are provided at n authentication servers. A number t2?t1 of the shares reconstruct the secret data. For a password attempt, the user computer communicates with at least t1 authentication servers to determine if the user password matches the password attempt and, if so, the user computer receives at least t2 secret data shares from respective authentication servers. The user computer uses the secret data to generate, with T?t1 of said t1 servers, a cryptographic token for authenticating the user computer to a selected verifier server, secret from said at least T servers, under said username.

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: Methods and systems are provided for authenticating a message ?, at a user computer of a group signature scheme, to a verifier computer. The method includes, at the user computer, storing a user id m for the user computer and a user signing key which comprises a signature on the user id m under a secret key of a selectively-secure signature scheme. The user id m is an element of a predetermined subring, isomorphic to q[x]/(g(x)), of a ring R=q[x]/(f(x)), where f(x) and g(x) are polynomials of degree deg(f) and deg(g) respectively such that deg(f)>deg(g)>1. The method includes, at the user computer, generating a first cryptographic proof ?1 comprising a zero-knowledge proof of knowledge of the user signing key and including the message ? in this proof of knowledge. The user computer sends the message ? and a group signature, comprising the first proof ?1, to the verifier computer.