“…There are many reports which assess either template aging or permanence that operate at the level of a complete biometric system rather than at the level of single features [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] which is our interest here. For example, one recent paper [ 19 ] proposes a new method for measuring biometric permanence.…”