Patent ID: 8490164
Filing Date: 2013-07-16
Classification: G06F

Abstract:
1. A user authentication method for authenticating a user at a first device communicating with a second device, the method comprising: when registering passwords, dividing secret information into a plurality of secret fragments by a threshold secret sharing scheme in the first device, the secret information being shared with the second device in advance; generating a plurality of cryptographic fragments by encrypting the plurality of secret fragments using a first plurality of secret keys that are uniquely and respectively set for each of the secret fragments, the secret keys being respectively generated from a first plurality of user passwords; and transmitting the generated plurality of cryptographic fragments from the first device to the second device for storage; when authenticating the user, receiving at the first device the plurality of cryptographic fragments transmitted from the second device; generating a plurality of secret fragment candidates by decrypting the received plurality of cryptographic fragments using a second plurality of secret keys generated from a second plurality of user passwords; generating a secret information candidate by the threshold secret sharing scheme using a group of the generated plurality of secret fragment candidates, the threshold secret sharing scheme based on a threshold number of user passwords; obtaining a verifying information candidate from the generated secret information candidate; transmitting the obtained verifying information candidate from the first device to the second device for comparison with verifying information stored in advance in the second device; and successfully decrypting the secret information when a number of the plurality of secret fragment candidates exceeds the threshold number in the threshold secret sharing scheme.