5812-DS00-R datasheet(17/84 Pages) BOARDCOM

17 / 84 page

Advance Data Sheet

BCM5812

3/11/03

B roa dcom Co rpo rat ion

Document

5812-DS01-405-R

Cryptographic Operations

Page 9

Figure 8 on page 11 shows a packet description for combined IPsec ESP encryption and authentication. The total packet

length is supplied in the packet descriptor. The offset is supplied in the command context in terms of 32-bit words (not bytes).

The IV is also supplied in the command context, copied there from the packet by the host software.

Figure 9 on page 12 shows an example of a logically contiguous input packet that is physically discontinuous in host

memory, requiring the BCM5812 to gather three input fragments. Three input fragment chain entry descriptors are shown,

organized as a linked list. Each fragment chain entry includes the address and length of the input fragment, along with a next

input fragment chain entry pointer.

The first input fragment chain entry is supplied in the packet descriptor structure. Subsequent input fragment chain entries

are read in by the BCM5812 as needed.

The length of the data to be encrypted or decrypted is the packet length (from the packet descriptor) minus the offset in bytes

(the offset value from the command context must be multiplied by 4).

Note

On some platforms, this may require each 32-bit word to be byte swapped.

Note

•

The total of the lengths in the input fragment chain entries must match the packet length.

•

Input fragment chain entries must be 32-bit aligned in host memory.

•

Input fragment buffers can be byte aligned in host memory.

•

The total length of the input for encryption or decryption must be a multiple of the cipher block size

(8 bytes for 3DES or DES).

5812-DS00-R Folha de dados(PDF) 17 Page - Broadcom Corporation.