STMicroelectronics STM32WL5 Series User Manual

RM0453 Rev 5 705/1450
RM0453 Public key accelerator (PKA)
720
24.4.7 Modular inversion
Modular inversion operation consists in the computation of multiplicative inverse A
-1
mod n.
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 Table 152.
Table 150. Modular exponentiation (normal mode)
Parameters with direction Value (Note) Storage Size
IN MODE 0x00 PKA_CR 6 bits
IN
Exponent length (in bits, not null) RAM@0x400
32 bits
Operand length (in bits, not null) RAM@0x404
IN/OUT
Operand A (base of
exponentiation)
(0 ≤ A < n) RAM@0xA44
ROS
IN
Exponent e (0 ≤ e < n) RAM@0xBD0
Modulus value n (Odd integer only, n < 2
3136
)RAM@0xD5C
OUT Result: A
e
mod n (0 ≤ result < n) RAM@0x724
Table 151. Modular exponentiation (fast mode)
Parameters with direction Value (Note) Storage Size
IN MODE 0x02 PKA_CR 6 bits
IN
Exponent length (in bits, not null) RAM@0x400
32 bits
Operand length (in bits, not null) RAM@0x404
IN/OUT
Operand A (base of
exponentiation)
(0 ≤ A < n) RAM@0xA44
ROS
IN
Exponent e (0 ≤ e < n) RAM@0xBD0
Modulus value n (Odd integer only, n < 2
3136
)RAM@0xD5C
IN/OUT
Montgomery param
R2 mod n
(mandatory) RAM@0x594
OUT Result: A
e
mod n (0 ≤ result < n) RAM@0x724
Table 152. Modular inversion
Parameters with direction Value (Note) Storage Size
IN
MODE 0x08 PKA_CR 6 bits
Operand length (In bits, not null) RAM@0x404 32 bits
Operand A (0 ≤ A < n) RAM@0x8B4
ROSModulus value n (Odd integer only, n < 2
3136
)RAM@0xA44
OUT Result: A
-1
mod n 0 < result < n RAM@0xBD0

STMicroelectronics STM32WL5 Series Specifications

General

Brand	STMicroelectronics
Model	STM32WL5 Series
Category	Microcontrollers
Language	English