Encryption apparatus
US4953211A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 5, 1989 |
| Grant date | Aug 28, 1990 |
| Priority date | — |
| Expiry date | Jul 5, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04K1/06
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Encryption apparatus mainly intended for encrypting speech signals samples a signal to be encrypted at two differing rates, and reads the sampled signal into storage means at one of said rates and reads it out of said storage at the other of said rates so that the signal is alternately dispersed upwardly and downwardly with each pair of upward and downward dispersion representing a frame. To improve security the apparatus further generates a pseudo random binary number, defines a superframe structure consisting of a predetermined number of said frames, and sets the starting point of each individual superframe as an upward or a downward dispersion in dependence on the next digit of said pseudo-random binary number.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.