Ecc F2 M Montgomery Modular Multiplication ((A × B × R-1) Mod N) - Motorola DigitalDNA MPC180E User Manual

ECC Routines
7.3.11 ECC F
2
Field addition in F m (polynomial-basis) may be performed on any two vectors loaded into
2
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
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.
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 The function operates the same regardless of whether or not the operands are in the Montgomery
conditions residue system.
Initial Condition
irred. poly. (if N0 selected)
Figure 7-14. F
7-22
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
m Add (Subtract)
m, this function provides identical results for both addition as
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Table 7-15. F m Modular Add (Subtract)
2
F m Modular Add (Subtract)
2
B3
B2
B1
B0
E (if B0 selected)
A3
A2
A1
D (if A0 selected)
A0
N3
N2
N1
N0
ECC
'1' - ECC enabled
EXP(k)
XYZ
'1' - F m enabled F2M
2
regAsel
set (00, 01, 10, 11)
regBsel
set (00, 01, 10, 11)
regNsel
set (00, 01, 10, 11)
Modsize
set
EXP(k)_SIZE
m Modular Add (Subtract) Register Usage
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MPC180E Security Processor User's Manual
Final Condition
?
?
?
C (if B0 selected)
?
?
?
irred. poly. (if N0 selected)
same
same
same
same
same
same