System for encrypting documents with stencils
US6728376B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 22, 1999 |
| Grant date | Apr 27, 2004 |
| Priority date | — |
| Expiry date | Dec 22, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09C5/00
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A symmetric key encryption system includes a printer or copier for performing decryption in two passes. During a first pass an encrypted image is decrypted to define a first partially decrypted image and during a second pass a complement of the encrypted image is decrypted to define a second partially decrypted image. The first partially decrypted image is formed when the encrypted image is rendered onto a first recording medium through a stencil. The stencil, which is a random arrangement of holes, is overlaid on the first recording medium to permit only selected portions of the encrypted image to be rendered on the recording medium. During the second pass, the complement of the encrypted image is rendered on a second recording medium through a complement of the stencil to yield the second partially decrypted image. Overlaying and aligning the first partially decrypted image and the second partially decrypted image finally decrypts the encrypted image.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.