Datasheet

PUKCL(u2Options) = PUKCL_EXPMOD_REGULARRSA | PUKCL_EXPMOD_WINDOWSIZE_2;
The following table describes the PrimeGen service features available from the various options.
Table 43-57. PrimeGen Service Options
Option Method Used
PUKCL_PRIMEGEN_TEST This option is used to specify that only tests will be made
on the provided number.
When this option is not specified, a prime generation
algorithm is selected, starting from the given seed and
incrementing it.
PUKCL_EXPMOD_WINDOWSIZE_1,2,3 or
4
Depending on this option, different bit-window sizes will
be used. For long exponents, the bigger the window, the
faster the computation. However, this has also an impact
on the size of the precomputations table.
For this service, two exclusive Calculus Modes are possible. The following table describes the Calculus
Mode Options.
Table 43-58. PrimeGen Service Calculus Mode Options
Option Explanation
PUKCL_EXPMOD_FASTRSA Perform a Fast computation.
PUKCL_EXPMOD_REGULARRSA Performs a Regular computation, slower than the Fast version, but
using regular calculus methods.
The length of the Precomp area depends on the window size W and u2NLength. The Precomp area
length is:
PrecompLen = max( 2*(u2NLength + 4) + 2W-1 * (u2NLength + 4), u2NLength + 8 + 64) + 8
Note: Please calculate precisely the length PrecompLen with the formula and the max() macro, which
takes a maximum of two values.
The following table shows the size of the precomputation workspace (PrecompLen), depending on the
chosen window size option.
Table 43-59. PrimeGen Service Precomputation Space Size
Option Specified Size of the PrecompBase
Workspace (bytes)
Content of the
Workspace
PUKCL_EXPMOD_WINDOWSIZE_1 max( 3*(u2NLength + 4), u2NLength
+ 72) + 8
x
PUKCL_EXPMOD_WINDOWSIZE_2 max( 4*(u2NLength + 4), u2NLength
+ 72) + 8
x x
3
PUKCL_EXPMOD_WINDOWSIZE_3 max( 6*(u2NLength + 4), u2NLength
+ 72) + 8
x x
3
x
5
x
7
SAM D5x/E5x Family Data Sheet
Public Key Cryptography Controller (PUKCC)
© 2019 Microchip Technology Inc.
Datasheet
DS60001507E-page 1499