Table 147. Modular Addition; Table 148. Modular Subtraction - ST STM32WL55JC Reference Manual

Public key accelerator (PKA)
Parameters with direction
IN
IN
IN/OUT
IN
OUT
Parameters with direction
IN
IN
IN/OUT
IN
IN/OUT
OUT
24.4.7 Modular inversion
Modular inversion operation consists in the computation of multiplicative inverse A
If the modulus n is prime, for all values of A (1 ≤ A < n) modular inversion output is valid. If
the modulus n is not prime, A has an inverse only if the largest common divisor between A
and n is 1.
If the operand A is a divisor of the modulus n, the result is a multiple of a factor of n.
Operation instructions for modular inversion are summarized in
Parameters with direction
IN
OUT
706/1454
Table 150. Modular exponentiation (normal mode)
MODE 0x00
Exponent length (in bits, not null)
Operand length (in bits, not null)
Operand A (base of
(0 ≤ A < n)
exponentiation)
Exponent e (0 ≤ e < n)
Modulus value n (Odd integer only, n < 2
e
Result: A mod n (0 ≤ result < n)
Table 151. Modular exponentiation (fast mode)
MODE 0x02
Exponent length (in bits, not null)
Operand length (in bits, not null)
Operand A (base of
(0 ≤ A < n)
exponentiation)
Exponent e (0 ≤ e < n)
Modulus value n (Odd integer only, n < 2
Montgomery param
(mandatory)
R2 mod n
e
Result: A mod n (0 ≤ result < n)
Table 152. Modular inversion
MODE 0x08
Operand length (In bits, not null)
Operand A (0 ≤ A < n)
Modulus value n (Odd integer only, n < 2
-1
Result: A mod n 0 < result < n
Value (Note)
3136
Value (Note)
3136
Value (Note)
3136
RM0453 Rev 2
Storage
PKA_CR
RAM@0x400
RAM@0x404
RAM@0xA44
RAM@0xBD0
) RAM@0xD5C
RAM@0x724
Storage
PKA_CR
RAM@0x400
RAM@0x404
RAM@0xA44
RAM@0xBD0
) RAM@0xD5C
RAM@0x594
RAM@0x724
Table 152.
Storage
PKA_CR
RAM@0x404
RAM@0x8B4
) RAM@0xA44
RAM@0xBD0
RM0453
Size
6 bits
32 bits
ROS
Size
6 bits
32 bits
ROS
-1
mod n.
Size
6 bits
32 bits
ROS