A method for updating biometric authentication data in an enrollment database, the method comprising: authenticating an input image using the enrollment DB over a first length of time, the authentication including: generating information for authenticating the input image, wherein the information for authenticating the input image comprises correlations in overlap regions between the input image and enrolled images in the enrollment DB, and sizes of the overlap regions between the input image and the enrolled images; calculating an authentication score based on the generated correlations in overlap regions between the input image and enrolled images in the enrollment DB; and accepting the authentication if the calculated authentication score is greater than an authentication threshold; storing the generated information for authenticating the input image in a memory;estimating the first length of time used for authenticating the input image; predicting a second length of time which is available for updating the enrollment DB wherein the second length of time is the difference between a determined maximum allowed time within which the authenticating and updating are to be performed and the estimated first length of time; and updating the enrollment DB during the second length of time such that the authenticating and updating are performed within the determined maximum allowed time, wherein the updating comprises: calculating a score from the generated correlations in overlap regions between the input image and enrolled images in the enrollment DB and the generated sizes of the overlap regions between the input image and the enrolled images; and enrolling the input image in the enrollment DB if the calculated score is larger than a determined threshold,. authenticating an input image using the enrollment DB over a first length of time, the authentication including: generating information for authenticating the input image, wherein the information for authenticating the input image comprises correlations in overlap regions between the input image and enrolled images in the enrollment DB, and sizes of the overlap regions between the input image and the enrolled images; calculating an authentication score based on the generated correlations in overlap regions between the input image and enrolled images in the enrollment DB; and accepting the authentication if the calculated authentication score is greater than an authentication threshold; generating information for authenticating the input image, wherein the information for authenticating the input image comprises correlations in overlap regions between the input image and enrolled images in the enrollment DB, and sizes of the overlap regions between the input image and the enrolled images; calculating an authentication score based on the generated correlations in overlap regions between the input image and enrolled images in the enrollment DB; and accepting the authentication if the calculated authentication score is greater than an authentication threshold; storing the generated information for authenticating the input image in a memory;estimating the first length of time used for authenticating the input image; predicting a second length of time which is available for updating the enrollment DB wherein the second length of time is the difference between a determined maximum allowed time within which the authenticating and updating are to be performed and the estimated first length of time; and updating the enrollment DB during the second length of time such that the authenticating and updating are performed within the determined maximum allowed time, wherein the updating comprises: calculating a score from the generated correlations in overlap regions between the input image and enrolled images in the enrollment DB and the generated sizes of the overlap regions between the input image and the enrolled images; and enrolling the input image in the enrollment DB if the calculated score is larger than a determined threshold,. calculating a score from the generated correlations in overlap regions between the input image and enrolled images in the enrollment DB and the generated sizes of the overlap regions between the input image and the enrolled images; and enrolling the input image in the enrollment DB if the calculated score is larger than a determined threshold,.