Cryptographic apparatus and method
US4200770A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 6, 1977 |
| Grant date | Apr 29, 1980 |
| Priority date | — |
| Expiry date | Sep 6, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2209/60
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A cryptographic system transmits a computationally secure cryptogram over an insecure communication channel without prearrangement of a cipher key. A secure cipher key is generated by the conversers from transformations of exchanged transformed signals. The conversers each possess a secret signal and exchange an initial transformation of the secret signal with the other converser. The received transformation of the other converser's secret signal is again transformed with the receiving converser's secret signal to generate a secure cipher key. The transformations use non-secret operations that are easily performed but extremely difficult to invert. It is infeasible for an eavesdropper to invert the initial transformation to obtain either conversers' secret signal, or duplicate the latter transformation to obtain the secure cipher key.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.