Patent ID: 9071598
Filing Date: 2015-06-30
Classification: H04L

Abstract:
1. A computer-implemented cryptographic method comprising performing, by a first computer entity, at least part of an authentication operation in which the first computer entity checks whether or not a second computer entity knows a predefined secret password π as a value whose knowledge is to be proven in the authentication operation, wherein each of the first and second computer entities comprises a computer processor executing associated computer instructions and operating on associated data; said at least part of the authentication operation comprising the first computer entity performing the following operations in interacting with the second computer entity: determining, from the password π known to the first computer entity as a value whose knowledge is to be proven in the authentication operation, a first position in a database, wherein the first position depends on the password π and wherein the first position and the password π are not revealed by the first computer entity to the second computer entity, and determining data in the first position in the database; executing a protocol in which the first computer entity receives one or more queries for data in the database, the queries being for data in a second position in the database, wherein if the password π is known to the second computer entity and is used by the second computer entity to determine the second position then the second position is the same as the first position, the queries not informing the first computer entity of the second position nor of the password π, wherein the first computer entity provides the data in the second position to the second computer entity without knowing the second position; checking whether or not the second computer entity knows the value π as a value whose knowledge is to be proven in the authentication operations, wherein checking whether or not the second computer entity knows the password π as a value whose knowledge is to be proven in the authentication operation comprises: the first computer entity receiving data from the second computer entity for use in checking whether or not the first position is the same as the second position, the received data not revealing the password π nor the second position to the first computer entity; and the first computer entity checking from the received data whether or not the first position is the same as the second position.