5812-DS01-R datasheet(19/84 Pages) BOARDCOM

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Advance Data Sheet

BCM5812

3/11/03

B roa dcom Co rpo rat ion

Document

5812-DS01-405-R

Cryptographic Operations

Page 11

The output byte order of encrypted or decrypted data is the same as that specified or configured for the input.

If authentication is performed, the HMAC value is written to the address specified in the next output fragment chain entry

address of the last output fragment chain entry. The full HMAC hash output is always written, which for MD5 is16 bytes, and

for SHA-1 is 20 bytes. That is, the returned authentication result is not truncated by the BCM5812 to 12 bytes as used by

HMAC-MD5-96 (RFC 2405) or HMAC-SHA1-96 (RFC2404).

Figure 8: Packet Description for IPsec DES/3DES Encryption and Authentication

The output byte order for the HMAC is the same as that specified or configured for encrypted or decrypted data.

If authentication is performed without encryption or decryption, the host software must set the offset in the command context

to zero. The BCM5812 writes the HMAC starting at the address given in the next output fragment chain entry in the packet

descriptor structure. The output fragment address in the packet descriptor is ignored.

If encryption is performed without authentication, the host software should set the offset in the command context to zero for

backward compatibility with the BCM582x. The BCM5812 ignores the next output fragment chain entry pointer in the last

output fragment chain entry.

BYTE 1

BYTE 0

BYTE 3

BYTE 2

Data, IV Byte Order

BYTE 5

BYTE 4

BYTE 7

BYTE 6

BYTE 9

BYTE 8

BYTE 11

BYTE 10

BYTE 13

BYTE 12

BYTE 15

BYTE 14