Datasheet

• the indication of the presence of the scalars in system RAM
Note: Please check precisely if one part of the scalars is in Crypto RAM. If this is the case, the
PUKCL_ZPECCMUL_SCAL_IN_CLASSIC_RAM option must not be used.
The u2Options number is calculated by an “Inclusive OR” of the options. Some Examples in C language
are:
• // Scalars are in system RAM
// The Point A window size is 3
// The Point B window size is 4
PUKCL(u2Options) = PUKCL_ZPECCMUL_SCAL_IN_CLASSIC_RAM |
PUKCL_ZPECCMUL_WINSIZE_A_VAL_TO_OPT(3) |
PUKCL_ZPECCMUL_WINSIZE_B_VAL_TO_OPT(4);
• // Scalars are in the PUKCC Cryptographic RAM
// The Point A window size is 2
// The Point B window size is 5
PUKCL(u2Options) = PUKCL_ZPECCMUL_WINSIZE_A_VAL_TO_OPT(2) |
PUKCL_ZPECCMUL_WINSIZE_B_VAL_TO_OPT(5);
For this service, many window sizes are possible. The window sizes in bits are those of the windowing
method used for the scalar multiplying.
The choice of the window sizes is a balance between the size of the parameters and the computation
time:
• Increasing the window size increases the precomputation table size.
• Increasing the window size to the optimum reduces the computation time.
The following table details the size of the point and the precomputation table, depending on the chosen
window size option.
Table 43-75. ZpEccQuickDualMulFast Service Window Size Options and Precomputation Table
Size
Option Specified Size of the Point and the
Precomputation Table
PUKCL_ZPECCMUL_WINSIZE_A_VAL_TO_OPT(WA) WA in [2,
15]
(3*(u2ModLength + 4)) * (2
(WA-2)
)
PUKCL_ZPECCMUL_WINSIZE_B_VAL_TO_OPT(WB) WB in [2,
15]
(3*(u2ModLength + 4)) * (2
(WB-2)
)
The scalars can be located in PUKCC RAM or in system RAM. If both scalars are entirely in system RAM
with no part in PUKCC RAM this can be signaled by using the option
PUKCL_ZPECCMUL_SCAL_IN_CLASSIC_RAM. In all other cases this option must not be used.
The following table describes this option.
SAM D5x/E5x Family Data Sheet
Public Key Cryptography Controller (PUKCC)
© 2019 Microchip Technology Inc.
Datasheet
DS60001507E-page 1520