
Public key accelerator (PKA)
RM0453
698/1454
RM0453 Rev 2
PKA operating modes
The list of operations the PKA can perform is detailed in
,
respectively, for integer arithmetic functions and prime field (Fp) elliptic curve functions.
Each of these operating modes has an associated code that has to be written to the MODE
field in the PKA_CR register.
Montgomery space and fast mode operations
For efficiency reason the PKA internally performs modular multiply operations in the
Montgomery domain, automatically performing inward and outward transformations.
As Montgomery parameter computation is time consuming the application can decide to use
a faster mode of operation, during which the precomputed Montgomery parameter is
Table 144. PKA integer arithmetic functions list
PKA_CR.MODE[5:0]
Performed operation
Reference
Hex
Binary
0x01
000001
Montgomery parameter computation R2 mod n
0x0E
001110
Modular addition (A+B) mod n
0x0F
001111
Modular subtraction (A-B) mod n
0x10
010000
Montgomery multiplication (AxB) mod n
0x00
000000
Modular exponentiation A
e
mod n
0x02
000010
Modular exponentiation A
e
mod n (fast mode)
0x08
001000
Modular inversion A-1 mod n
0x0D
001101
Modular reduction A mod n
0x09
001001
Arithmetic addition A+B
0x0A
001010
Arithmetic subtraction A-B
0x0B
001011
Arithmetic multiplication AxB
0x0C
001100
Arithmetic comparison (A=B, A>B, A<B)
0x07
000111
RSA CRT exponentiation
Table 145. PKA prime field (Fp) elliptic curve functions list
PKA_CR.MODE[5:0]
Performed operation
Reference
Hex
Binary
0x28
101000
Point on elliptic curve Fp check
0x20
100000
ECC scalar multiplication kP
0x22
100010
ECC scalar multiplication kP (fast mode)
0x24
100100
ECDSA sign
0x26
100110
ECDSA verification