7.4.4.4 Last Output Data Mode (CBC-MAC)

This mode is used to generate cryptographic checksums on data (MAC) using a CBC-MAC or a CFB encryption algorithm (refer to FIPS Publication 81 Appendix F).

The CMAC algorithm is a variant of CBC-MAC with post-processing requiring one-block encryption in ECB mode. Thus CBC-MAC is useful to accelerate CMAC.

After each end of encryption/decryption, the output data is available either on the output data registers for Manual and Auto modes or at the address specified in the receive buffer pointer for DMA mode (see Table 7-8).

TDES_MR.LOD can be used to retrieve only the last data of several encryption/decryption processes.

This data is only available in TDES_ODATARx.

Therefore, there is no need to define a read buffer in DMA mode.