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Table 7-5. ECC F
Post-conditions
B1 = X
/ X'
2
B2 = Y
/ Y'
2
B3 = Z
/ Z'
2
A2 = undefined (when XYZ = 1) or Z
A3 = undefined (when XYZ = 1) or Z
Unless explicitly noted, all other registers are not guaranteed to be any particular value.
Special
—
conditions
Initial Condition
Figure 7-4. ECC F
It is important to note that unlike the RSA exponentiation routine, the point to be multiplied
is not expected to be in the Montgomery residue system when loaded into the PKEU. All
of the other ECC parameters are also expected to be loaded in standard format. This
includes the a and b parameters of the ECC system. In addition, the "R
also required. This term is used by the PKEU to put the operands in the Montgomery
residue system. See the full description of this function/value below.
It is the responsibility of the host processor to provide multiplier data to the PKEU during
the operation. That is, the 'k' from the point multiplication 'kP' must be provided
dynamically by the host micro-processor in 32-bit words. Note that the host must supply
the k data starting with the most significant 32-bit word and working down to the least
significant word. Each individual word, however, is formatted msb to lsb (i.e.
"k_word[msb:lsb]").
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Point Multiply (Continued)
p
F
2
2
2
2
(when XYZ = 0)
2
3
(when XYZ = 0)
2
B3
B2
2
R
mod N
B1
B0
b
a
A3
1 (or Z
)
A2
1
y
(or Y
)
A1
1
1
x
(or X
)
A0
1
1
N3
N2
N1
N0
prime p
ECC
'1' - ECC enabled
k (run-time)
EXP(k)
XYZ
select '1' or '0'
F2M
'0' - F
enabled
p
Modsize
set
set
EXP(k)_SIZE
Point Multiply Register Usage
p
Chapter 7. Public Key Execution Unit
Point Multiply
p
Final Condition
Z
(or Z'
)
2
2
Y
(or Y'
)
2
2
X
(or X'
)
2
2
?
3
? (or Z
)
2
2
? (or Z
)
2
?
?
?
?
?
prime p
same
?
same
same
same
same
ECC Routines
2
mod N" term is
7-9
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