9. A method according to claim 1 , wherein: applying the function to each hash value includes initiating the aggregate hash value as a constant, incrementally applying the function to each hashed statement to create therefrom a new aggregate hash value, and repeating application of the function until all hashed statements and the constant are represented by the aggregate hash value; and wherein the function is both associative and commutative.
9. A method according to claim 1 , wherein: applying the function to each hash value includes initiating the aggregate hash value as a constant, incrementally applying the function to each hashed statement to create therefrom a new aggregate hash value, and repeating application of the function until all hashed statements and the constant are represented by the aggregate hash value; and wherein the function is both associative and commutative. 11. A method according to claim 9 , wherein the constant is a secret key, and repeating the application of the function yields an aggregate hash value that is dependent upon both of the secret key and all hashed statements.