Abstract: The subject matter discloses a method operated on at least two servers for a third-party client, the method comprising receiving by a first server a first result of the first irreversible function applied to a secret key from a first third-party client, receiving by a second server a second result of the second irreversible function applied to the secret key from the third-party client, receiving by the first server, a message from a second third-party client, the first server computing a first hash function on said first result and on said message, and sending a result of the first hash function from the first server to the second server, the second server computing a second hash function on said second result and on the result of the first hash function sent from first server and outputting the result generated by second server as HMAC result.

Abstract: The subject matter discloses a computerized system, comprising a computerized device communicating with a third party server, that comprises a memory unit that stores a representation of a Boolean circuit and a processing unit for calculating a result of the Boolean circuit according to a string used as input for the Boolean circuit and calculating a first predefined function on the result of the Boolean circuit. The system also comprises a first auxiliary server communicating with the computerized device, the first auxiliary server comprises a processing unit for calculating a second predefined function on the result of the Boolean circuit received from the computerized device and a second auxiliary server communicating with the computerized device comprises a processing unit for comparing the result of the first predefined function and the result of the second predefined function.

Abstract: The subject matter discloses a method operated on at least two servers for a third-party client, the method comprising receiving by a first server a first result of the first irreversible function applied to a secret key from a first third-party client, receiving by a second server a second result of the second irreversible function applied to the secret key from the third-party client, receiving by the first server, a message from a second third-party client, the first server computing a first hash function on said first result and on said message, and sending a result of the first hash function from the first server to the second server, the second server computing a second hash function on said second result and on the result of the first hash function sent from first server and outputting the result generated by second server as HMAC result.