Securing the implementation of a cryptographic process using key expansion
US8966279B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 21, 2010 |
| Grant date | Feb 24, 2015 |
| Priority date | — |
| Expiry date | Dec 29, 2032 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2209/24
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
In the field of computer enabled cryptography, such as a keyed block cipher having a plurality of rounds, the cipher is hardened against an attack by protecting the cipher key by means of a key expansion process which obscures the cipher and/or the round keys by increasing their lengths to provide an expanded version of the keys for carrying out encryption or decryption using the cipher. This is especially advantageous in a “White Box” environment where an attacker has full access to the cipher algorithm, including the algorithm's internal state during its execution. This method and the associated computing apparatus are useful where the key is derived through a process and so is unknown when the software code embodying the cipher is compiled. This is typically the case where there are many users of the cipher and each has his own key, or where each user session has its own key.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.