Freescale Semiconductor MPC8313E PowerQUICC II Pro Family Reference Manual page 647

14.1.2 Execution Units (EUs)
'Execution unit' (EU) is the generic term for a functional block that performs the mathematical
manipulations required by protocols used in cryptographic processing. The EUs are compatible with
IPSec, SSL/TLS, iSCSI, SRTP, and 802.11i processing, and can work together to perform high-level
cryptographic tasks. The SEC's execution units are as follows:
• DEU for performing block cipher, symmetric key cryptography using DES and 3DES
• AESU for performing the advanced encryption standard algorithm
• MDEU for performing security hashing using MD-5, SHA-1, SHA-224, or SHA-256
Each EU is described in detail in
14.1.2.1 Data Encryption Standard Execution Unit (DEU)
The DES execution unit (DEU) performs bulk data encryption/decryption, in compliance with the data
encryption standard algorithm (ANSI x3.92). The DEU can also compute 3DES, an extension of the DES
algorithm in which each 64-bit input block is processed three times. The SEC 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 SEC supports two modes of operation: electronic code book (ECB) and cipher clock chaining
(CBC).
For more information, refer to
14.1.2.2 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.
AESU is a symmetric-key algorithm; the sender and receiver use the same key for both encryption and
decryption. The session key and IV 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, CTR,
and CCM modes.
For more information, refer to
14.1.2.3 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, SHA-224, 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.
• The MD5 generates a 128-bit hash, and the algorithm is specified in RFC 1321.
MPC8313E PowerQUICC™ II Pro Integrated Processor Family Reference Manual, Rev. 2
Freescale Semiconductor
Section 14.4, "Execution Units."
Section 14.4.1, "Data Encryption Standard Execution Unit (DEU).
Section 14.4.3, "Advanced Encryption Standard Execution Unit (AESU)."
Security Engine (SEC) 2.2
14-5