Method and apparatus for performing strong encryption or decryption data using special encryption functions
US6333983A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 16, 1997 |
| Grant date | Dec 25, 2001 |
| Priority date | — |
| Expiry date | Dec 16, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2209/56
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for decrypting an input block encrypted under a predetermined key in a cryptographic system having a cryptographic facility providing cryptographic functions for transforming blocks of data. The cryptographic functions include an encryption function for encrypting a block under a predetermined key and a transformation function for transforming a block encrypted under a first key to the same block encrypted under a second key. The cryptographic functions have at least one key pair with the property that successive encryption of a block under the keys of the pair regenerates the block in clear form. The input block is first transformed into an intermediate block encrypted under one of the key pair using the transformation function. The intermediate block is then further encrypted under the other of the key pair using the encryption function to generate an output block successively encrypted under the keys of pair, thereby to regenerate the input block in clear form. The invention is useful in cryptographic systems in which the decryption function being emulated by the transformation and encryption functions is unavailable for export control or other reasons.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.