Datasheet

Note:

Depending on the mode, there are other ways of clearing the DATRDY flag. See AES Interrupt Status

WARNING

In DMA mode, reading AES_ODATARx before the last data transfer may lead to unpredictable results.

57.4.4 Galois/Counter Mode (GCM)

57.4.4.1 Description

GCM comprises the AES engine in CTR mode along with a universal hash function (GHASH engine) that is defined

over a binary Galois field to produce a message authentication tag (the AES CTR engine and the GHASH engine are

depicted in the figure below

The GHASH engine processes data packets after the AES operation. GCM assures the confidentiality of data

through the AES Counter mode of operation for encryption. Authenticity of the confidential data is assured through

the GHASH engine. GCM can also provide assurance of data that is not encrypted. Refer to the NIST Special

Publication 800-38D for more complete information.

GCM can be used with or without the DMA master. Messages may be processed as a single complete packet of data

or they may be broken into multiple packets of data over time.

GCM processing is computed on 128-bit input data fields. There is no support for unaligned data. The AES key

length can be whatever length is supported by the AES module.

The recommended programming procedure when using DMAPDC is described in the section GCM Processing.

SAM E70/S70/V70/V71 Family

Advanced Encryption Standard (AES)

echnology Inc.

Datasheet

DS60001527D-page 1790