Datasheet

Multiplication without Accumulation or Subtraction
In the case the options bits specify that either an Accumulation or a subtraction should be performed, this
service performs the following operation:
R = (X × Y + CarryOperand)mod B
XLength + YLength
Table 43-28. Fmult Service Carry Settings
Option AND CARRYOPTIONS CarryOperand Resulting Operation
SET_CARRYOPTION(ADD_CARRY) CarryIn R = X*Y + CarryIn
SET_CARRYOPTION(SUB_CARRY) - CarryIn R = X*Y - CarryIn
SET_CARRYOPTION(ADD_1_PLUS_CARRY) 1 + CarryIn R = X*Y + 1 + CarryIn
SET_CARRYOPTION(ADD_1_MINUS_CARRY) 1 - CarryIn R = X*Y + 1 - CarryIn
SET_CARRYOPTION(CARRY_NONE) 0 R = X*Y
SET_CARRYOPTION(ADD_1) 1 R = X*Y + 1
SET_CARRYOPTION(SUB_1) - 1 R = X*Y - 1
SET_CARRYOPTION(ADD_2) 2 R = X*Y + 2
43.3.4.9.9 Status Returned Values
Table 43-29. Fmult Service Return Codes
Returned Status Importance Meaning
PUKCL_OK – Service functioned correctly
43.3.4.10 Square
43.3.4.10.1 Purpose
The purpose of this service is to compute the square of a big number and optionally accumulate/subtract
from a second big number.
Please note that this service uses an optimized implementation of the squaring. It also means that when
the GF(2
n
) flag is set, the execution time will be smaller than when not set (in that case, the squaring
execution time will still be smaller than for a standard multiplication).
The available options are as follows:
• Work in the GF(2
n
) or in the standard integer arithmetic field
• Add of a supplemental CarryOperand
• Overlapping of the operands is possible, taking into account some constraints
• Modular Reduction of the computation result
43.3.4.10.2 How to Use the Service
43.3.4.10.3 Description
This service provides the following (if not computing a modular reduction of the result):
R = [Z] ± (X
2
+ CarryOperand)
Or (if computing a modular reduction of the result):
R = ([Z] ± (X
2
+ CarryOperand))mod N
SAM D5x/E5x Family Data Sheet
Public Key Cryptography Controller (PUKCC)
© 2019 Microchip Technology Inc.
Datasheet
DS60001507E-page 1469