Device for secure read, write and read/modify/write operation with divided track transducer head
US6830183B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 1, 2003 |
| Grant date | Dec 14, 2004 |
| Priority date | — |
| Expiry date | May 1, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K7/084
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for placing and later determining the distance between transitions from a first logical state to a second logical state stored on a medium, for example, a document. This determination is used to precisely characterize the information pattern in order to authenticate the information and the medium on which the information is stored. The invention uses a reader having a leading and trailing read apparatus, which allow information to be read simultaneously from two or more locations spaced a known distance apart. The distance between the center lines of each read apparatus is preferably an odd integer multiple of one half the distance between logical clock transitions. The distance between a first transition at the leading read apparatus and a next transition at the trailing read apparatus is used as a reference, hence given the term the “Reference Value”. The Reference Value is compared with the distance between the first transition and a second transition on the medium. Detection of deviations in spacing between transitions is unaffected by variations if the velocity of the medium with respect to the reader. Thus, the present invention is a method …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.