MOTOROLA

MPC185 Security Processor Technical Summary

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algorithm in which each 64-bit input block is processed three times. The MPC185 supports 2 key (K1=K3)

or 3 key 3DES.

The DEU operates by permuting 64-bit data blocks with a shared 56-bit key and an initialization vector (IV).

The MPC185 supports two modes of IV operation: Electronic Code Book (ECB) and Cipher Clock

Chaining (CBC).

7.3 Arc Four Execution Unit (AFEU)

The AFEU accelerates a bulk encryption algorithm compatible with the RC4 stream cipher from RSA

Security, Inc. The algorithm is byte-oriented, meaning a byte of plain text is encrypted with a key to produce

a byte of ciphertext. The key is variable length and the AFEU supports key lengths from 40 to 128 bits (in

byte increments), providing a wide range of security strengths. RC4 is a symmetric algorithm, meaning each

of the two communicating parties share the same key.

7.4 Advanced Encryption Standard Execution Unit (AESU)

The AESU is used to accelerate bulk data encryption/decryption in compliance with the Advanced

Encryption Standard algorithm Rinjdael. The AESU executes on 128 bit blocks with a choice of key sizes:

128, 192, or 256 bits.

AESA is a symmetric key algorithm, the sender and receiver use the same key for both encryption and

decryption. The session key and IV(CBC mode) are supplied to the AESU module prior to encryption. The

processor supplies data to the module that is processed as 128 bit input. The AESU operates in ECB, CBC,

and counter modes.

7.5 Kasumi Execution Unit (KEU)

The KEU is used to accelerate two algorithms defined in the 3GPP architecture, a confidentiality algorithm

(f8) and an integrity algorithm (f9). Each of these algorithms is based on the Kasumi algorithm. Kasumi is

a block cipher that produces a 64-bit output from a 64-bit input under the control of a 128-bit key. The

confidentiality algorithm f8 is a stream cipher that is used to encrypt/decrypt blocks of data under a

confidentiality key. The block of data may be between 1 and 5114 bits long. The algorithm uses Kasumi in

a form of output-feedback mode as a keystream generator. The integrity algorithm f9 computes a 32-bit

message authentication code (MAC) of a given input message using an integrity key. The approach adopted

uses Kasumi in a form of CBC-MAC mode.

7.6 Message Digest Execution Unit (MDEU)

The MDEU computes a single message digest (or hash or integrity check) value of all the data presented on

the input bus, using either the MD5, SHA-1 or SHA-256 algorithms for bulk data hashing. With any hash

algorithm, the larger message is mapped onto a smaller output space, therefore collisions are potential, albeit

not probable. The 160-bit hash value is a sufficiently large space such that collisions are extremely rare. The

security of the hash function is based on the difficulty of locating collisions. That is, it is computation

infeasible to construct two distinct but similar messages that produce the same hash output.

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The MD5 generates a 128-bit hash, and the algorithm is specified in RFC 1321.

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SHA-1 is a 160-bit hash function, specified by the ANSI X9.30-2 and FIPS 180-1 standards.

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SHA-256 is a 256-bit hash function that provides 256 bits of security against collision attacks.

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The MDEU also supports HMAC computations, as specified in RFC 2104.

Freescale Semiconductor, Inc.

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