Patent ID: 8538014

Claim:
A method for computing a target secret S t in a sequence of secrets S 0 . . . S n , the method comprising: using a computer to perform operations for: obtaining k hash functions h 1 , . . . , h k ; obtaining one or more seeds (index 1 , S h1 ), . . . , (index k , S hk ) for hash functions h 1 , . . . , h k , respectively, wherein the first component in the seed, index, is the index of a secret S i , and the second component in the seed S hi is the value of that secret in the sequence of secrets S 0 . . . S n ; computing S t by starting with a seed which precedes S t , wherein the seed that precedes S t corresponds to a highest-order hash h i for which a corresponding index is not greater than t, and successively applying each hash function h k , . . . , h 1 a corresponding number of times to produce S t ; and storing S t in a computer memory; wherein the hash functions h 1 , . . . , h k are ordered, with h 1 being the lowest order hash function and h k being the highest order hash function, and applied in order from highest order to lowest order, wherein the index of the seed for a higher order hash function is greater than or equal to the indices of the seeds for lower order hash functions; wherein computing S t involves starting with the highest-order hash function's corresponding seed for which the index is not greater than t, and successively applying each hash function, starting with that hash function and proceeding sequentially through the lower-order hash functions to produce S t ; wherein, for each hash function, the number of times the hash function is applied to compute S t is determined using t and the index for the hash function; wherein hash functions h 1 , . . . , h k are associated with an increasing sequence of skip values sv 1 , . . . , sv k , respectively, wherein a given skip value sv i specifies how many secrets in the sequence the associated hash function h i (x) skips; and wherein for a given seed S hi in the one or more seeds S h1 , . . . , S hk , the associated index i is the smallest multiple of sv i which is greater than the index of the lowest-numbered existing secret S lowest .