Programming Model
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
26-151
26.5.10.2 AFEU Key Size Register (AFEUKSR)
The value in the AFEU Key Size Register (AFEUKSR) indicates the number of bytes of key
memory that should be used in performing S-box permutation. Any key data beyond the number
of bytes in the Key Size Register is ignored. This register is cleared when the AFEU is reset or
reinitialized. If the key size specified is less than 1 or greater than 16, a key size error is
generated. If the Key Size Register is modified during processing, a context error is generated.
Note:
Although the AFEU supports key lengths as short as 1 byte, a 1-byte key offers little
security. Most ARC-4 applications specify keys of 5–16 bytes.
The device driver creates properly formatted descriptors for situations requiring a key permute
prior to ciphering. When using core processor-controlled access (typically for debug), the user
must perform the following sequence:
1.
Configure the AFEU Mode Register to perform a permute with key
2.
Write the key data to AFEU key registers
3.
Write the key size to the Key Size Register.
The AFEU starts permuting the memory with the contents of the key registers immediately after
the key size is written.
AFEUKSR
AFEU Key Size Register
Offset 0xC8008
Bits
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
Field
—
Type
R/W
Reset 0x0000
Bits
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
Field
—
Type
R/W
Reset
0x0000
Bits 31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Field
—
Type
R/W
Reset 0x0000
Bits
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Field
—
Key Size
Type
R/W
Reset 0x0000
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...