7-22
MPC180E Security Processor User’s Manual
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
ECC Routines
7.3.11
ECC F
2
m Add (Subtract)
Field addition in F
2
m (polynomial-basis) may be performed on any two vectors loaded into
A (A0-A3) and B (B0-B3), where both of these vectors are less than the value stored in the
modulus (irreducible polynomial) register N (N0-N3). The results are stored in the
respective B register. In F
2
m, this function provides identical results for both addition as
well as subtraction, therefore, it is sufficient to support both of these functions with this
single routine. This function operates with a minimum of 4 digits (Modsize = 3).
Prior to initiating this function, the A, B, and N register pointers must be set in the Control
Register which indicate which sub-registers (e.g A0, B0, A1, B1, etc.) are the targeted
operands. See Control Register description for a detailed description. Once this is
performed, the host processor may successfully initiate this function.
Figure 7-14. F
2
m Modular Add (Subtract) Register Usage
Table 7-15. F
2
m Modular Add (Subtract)
F
2
m Modular Add (Subtract)
Computation
C = D + E mod N, where D, E, and C are integers and are less than N
Entry name
modularadd (same as with integer add)
Entry address
0x008(modularadd)
Pre-conditions
A0-3 = D (binary polynomial, exact A-location pre-selected in control register)
B0-3 = E (binary polynomial, exact B-location pre-selected in control register)
N0-3 = irreducible polynomial of the ECC system
Post-conditions
B0-3 = results of modular addition (subtraction) stored where the B operand was located
Unless explicitly noted, all other registers are not guaranteed to be any particular value.
Special
conditions
The function operates the same regardless of whether or not the operands are in the Montgomery
residue system.
N1
N2
N3
A0
A1
A2
A3
B0
B1
B2
B3
Initial Condition
Final Condition
?
?
?
N0
C (if B0 selected)
E (if B0 selected)
irred. poly. (if N0 selected)
irred. poly. (if N0 selected)
D (if A0 selected)
?
?
?
XYZ
F2M
EXP(k)
regAsel
regBsel
regNsel
‘1’ - F
2
m enabled
same
set (00, 01, 10, 11)
set (00, 01, 10, 11)
set (00, 01, 10, 11)
same
same
same
Modsize
EXP(k)_SIZE
set
same
ECC
same
‘1’ - ECC enabled
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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