5812-DS01-R datasheet(14/84 Pages) BOARDCOM

14 / 84 page

BCM5812

Advance Data Sheet

3/11/03

B roa dcom Co rpo rat ion

Page 6

Cryptographic Operations

Document

5812-DS01-405-R

Programming structures are described relative to a little endian host processor system, where the layout in host memory and

on the PCI bus is the same. See “Endian Considerations” on page 42 for a discussion of the differences on big endian

systems.

IPSEC 3DES

The BCM5812 performs FIPS-46-3 [11] compliant DES-CBC and 3DES-CBC bulk encryption and decryption, combined with

RFC-2104 [10] compliant SHA-1-HMAC or MD5-HMAC. These algorithms are the primary ones used for the IPsec

(RFC2401 [2]) ESP and AH Security protocols (RFC2406 [7] and RFC2402 [3], respectively). Cipher Block Chaining Mode

(CBC) is diagrammed in Figure 7, taken from NIST Special Publication 800-38A [16].

The SHA-1 provides features specifically to support the IPsec use of 3DES and DES as described in RFC2406 [7], and for

HMAC-SHA-1 (RFC-2404 [5]) and HMAC-MD5 (RFC2403 [4]). Figure 5 shows the command context structure used for

combined 3DES or DES encryption, with HMAC-SHA-1 or HMAC-MD5 authentication, for IPsec processing. The flags,

detailed in Table 4 on page 7, indicate the specific operations to be performed. The command context should always include

three DES keys, even for single DES, so that the length of this structure is always 80 bytes.

The command context supplies the keys, initialization vector (IV), and authentication contexts as shown in Figure 5. The

opcode for this command, which uses MCR1@, is 0x00.

Authentication contexts are partial HMAC calculations pre-computed using the authentication secret. Figure 6 on page 8

diagrams the computation for the HMAC inner and outer state. A 20 byte field is used for both the HMAC-SHA-1 and HMAC-

MD5 states. HMAC-MD5 only uses the first 16 bytes, and the remaining 4 bytes should be set to zeros.

Note

•

An MCR must contain at least one packet descriptor.

•

The minimum command context length actually read by the BCM5812 is 64 bytes.

Note

Broadcom supplies a software routine in the Software Reference Library for computing HMAC inner and

outer states.

5812-DS01-R 数据表(PDF) 14 Page - Broadcom Corporation.