Patent ID: 8200969

Claim:
A method for data verification by challenge, the method comprising: storing a data piece and a hash value of the data piece in a receiver; receiving, at the receiver, a hash value of a data piece stored in a sender; if the hash value of the data piece stored in the sender matches the hash value of the data piece stored in the receiver, then sending a challenge packet from the receiver to the sender, the challenge packet to identify via fields a position and a length of a non-fixed window over a subset of the data piece stored in the receiver; receiving, from the sender, a sample data set that is a subset of the data piece stored in the sender, wherein the sample data set is to be determined by the position and the length of the non-fixed window; comparing the sample data set with a receiver data set, the receiver data set being the subset of the data piece stored in the receiver corresponding with the non-fixed window; and performing a response based on the comparison of the sample data set and the receiver data set.