On Tuesday, Tumbleweed Communications Corporation obtained a U.S. patent on its new digital signature technology. U.S. Patent No. 7,073,056, a continuation patent entitled "Apparatus and Method for Demonstrating and Confirming the Status of Digital Certificates and Other Data,” includes only one method claim for generating an interval hash tree, which is described in the specification as being constructed “where leaf nodes correspond to ranges in the list [of data items].” The claimed method “for use in an electronic communications protocol for generating a cryptographically assured confirmation that a candidate data item does not belong to a plurality of data items” not including all of the data items in a confirmation, comprises the steps of “(a) storing in a memory device, a plurality of data items; (b) deriving a plurality of leaf nodes from said data items; (c) generating an interval hash tree by associating, said leaf nodes with a plurality of intermediate nodes and at least one root node; and (d) digitally signing said at least one root node.” According to the patent, “an object of the invention [is] to greatly reduce the processing effort, network bandwidth, network latency, data storage, and data replication requirements needed to determine whether a particular certificate has been revoked.” This is the 23rd U.S. patent issued to Tumbleweed Communications.

U.S. Patent No. 7,073,056: LINK
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Tumbleweed Press Release: LINK
Tumbleweed Communications Website: LINK