MOTOROLA

MPC185 Security Processor Technical Summary

7

6.6 Crypto-Channels

The MPC185 includes four crypto-channels that manage data and EU function. Each crypto-channel

consists of the following:

•

Control registers containing information about the transaction in process

•

A status register containing an indication of the last unfulfilled bus request

•

A pointer register indicating the location of a new descriptor to fetch

•

Buffer memory used to store the active data packet descriptor

Crypto-channels analyze the data packet descriptor header and requests the first required cryptographic

service from the controller. The controller implements a programmable prioritization scheme that allows the

user to dictate the order in which the four crypto-channels are serviced. After the controller grants access to

the required EU, the crypto-channel and the controller perform the following steps:

1. Set the appropriate mode bits available in the EU for the required service.

2. Fetch context and other parameters as indicated in the data packet descriptor buffer and use these

to program the EU.

3. Fetch data as indicated and place in either the EU input FIFO or the EU itself (as appropriate).

4. Wait for EU to complete processing.

5. Upon completion, unload results and context and write them to external memory as indicated by

the data packet descriptor buffer.

6. If multiple services requested, go back to step 2.

7. Reset the appropriate EU if it is dynamically assigned. Note that if statically assigned, a EU is

reset only upon direct command written to the MPC185.

8. Perform descriptor completion notification as appropriate. This notification comes in one of two

forms—interrupt or header writeback modification—and can occur at the end of every descriptor,

at the end of a descriptor chain, or at the end of specially designated descriptors within a chain.

7 Execution Units (EUs)

‘Execution unit’ is the generic term for a functional block that performs the mathematical permutations

required by protocols used in cryptographic processing. The EUs are compatible with IPsec, WAP/WTLS,

IKE, SSL/TLS and 3GPP processing, and can work together to perform high level cryptographic tasks. The

MPC185 execution units are as follows:

•

PKEU for computing asymmetric key operations, including Modular Exponentiation (and other

Modular Arithmetic functions) or ECC Point Arithmetic

•

DEU for performing block cipher, symmetric key cryptography using DES and 3DES

•

AFEU for performing RC-4 compatible stream cipher symmetric key cryptography

•

AESU for performing the Advanced Encryption Standard algorithm

•

KEU for performing F8 and F9 encryption and authentication

•

MDEU for performing security hashing using MD-3, SHA-1, or SHA-256

•

RNG for random number generation

7.1 Public Key Execution Unit (PKEU)

The PKEU is capable of performing many advanced mathematical functions to support both RSA and ECC

public key cryptographic algorithms. ECC is supported in both F(2)m (polynomial-basis) and F(p) modes.

This EU supports all levels of functions to assist the host microprocessor to perform its desired

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