Method and apparatus for facilitating efficient authenticated encryption
US7046802B2 · kind B2 · utility
Inventor
Key dates
| Filing date | Jul 30, 2001 |
| Grant date | May 16, 2006 |
| Priority date | — |
| Expiry date | Nov 20, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2209/20
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A block-cipher based encryption scheme providing both privacy and authenticity that encrypts an arbitrary-length message into a minimal-length ciphertext. In one embodiment, “OCB”, a message is encrypted using a nonce by partitioning it into 128-bit message blocks and a possibly shorter message fragment. A sequence of offsets is computed from the nonce and block cipher using shifts and conditional xors. Each message block is xored with an offset, enciphered, and xored with the offset, yielding a ciphertext block. The length of the message fragment is encoded, xored with an offset, enciphered to give a pad, truncated, and xored with the message fragment to give a ciphertext fragment. A checksum is formed by xoring the message blocks, the padded ciphertext fragment, and the pad. It is xored with an offset and enciphered to yield a tag. The ciphertext is the ciphertext blocks, the ciphertext fragment, and the tag.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.