R P R N Mod P Calculation - Motorola DigitalDNA MPC180E User Manual

Initial Condition
7.5.3 R R mod P Calculation
p N
The PKEU has the ability to calculate R
the number of digits of the modulus P, and E is the number of digits of the modulus N, and
D + 4 < E. This constant is used in performing Chinese Remainder Theorem calculations
given modulus N = P × Q, where P and Q are prime numbers. Although labelled R
P, this function can also compute R
requirement of the command, but a system requirement, as for all subfunctions of Chinese
Remainder Theorem to be executable on the PKEU, the number of digits of P and Q must
each be at least five.
As with the standard R
and only works with the Control Register F
To use this function, MOD_SIZE must be programmed with D-1, and EXP_SIZE must be
programmed with E-1, and the prime modulus (either P or Q) is written into memory N.
The complete set of I/O conditions is shown in Table 7-26.
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
B3
B2
B1
B0
A3
A2
A1
A0
N3
N2
N1
N0
modulus N(⇑)
ECC
'0' - ECC disabled
EXP(k)
XYZ
F2M
'0' - integer-modulo-n enabled
regAsel
regBsel
set (00)
set (00) regNsel
Modsize
set
EXP(k)_SIZE
2
Figure 7-23. R mod N Register Usage
R mod P, where R
p N
R mod Q. The requirement D + 4 < E is not a
Q N
2
mod N operation, this operation exists primarily to support RSA
M bit set to zero.
2
Chapter 7. Public Key Execution Unit
Miscellaneous Routines
Final Condition
2
R mod N(⇑)
modulus N(⇑)
same
same
same
16D
= 2 , and R
p
16E
= 2 ; D is
N
R mod
P N
7-33