Datasheet

43.3.5.1.7 Modular Reductions Service Parameters Definition
Table 43-44. RedMod Service Parameters
Parameter Type Direction Location Data Length Before
Executing the
Service
After Executing
the Service
u2Options u2 I – – Options (see
below)
Options (see
below)
Specific/CarryIn Bits I – – Must be set to
zero.
–
Specific/Gf2n Bit I – – GF(2
n
) Bit –
Specific/
CarryOut Zero
Violation
Bits I – – – Carry Out, Zero
Bit and Violation
Bit filled
according to the
result
nu1ModBase
( see Note 1)
nu1 I Crypto
RAM
u2ModLength + 4 Base of N Base of N
untouched
nu1CnsBase nu1 I Crypto
RAM
u2ModLength + 12 Base of Cns Base of Cns
filled with the
Setup Constant
u2ModLength u2 I – – Length of N Length of N
nu1RBase nu1 I Crypto
RAM
GF(p): 64 bytes
GF(2n): 68 bytes
Base of R
as a workspace
Base of R
workspace
corrupted
nu1XBase (see
Note 2)
nu1 I Crypto
RAM
2*u2ModLength
+ 8
Base of X as a
workspace
Base of X
workspace
corrupted
Note:
1. The Modulus is to be given as a u2ModLength Aligned Significant Length Bytes however, it has to
be provided as a u2ModLength + 4 bytes long number, having the four high-order bytes set to zero.
2. Before the X (pointed by {nu1XBase,2 * u2ModLength + 8}) LSB bytes, four supplementary bytes
will be saved/restored. Other four supplementary bytes will also be saved/restored after the X MSB
bytes. All these supplementary bytes may be entirely in the Crypto RAM (therefore, do not place
the X area too near the end of the Crypto RAM) and shall not overlap with other area used by the
service.
SAM D5x/E5x Family Data Sheet
Public Key Cryptography Controller (PUKCC)
© 2019 Microchip Technology Inc.
Datasheet
DS60001507E-page 1487