Datasheet

...........continued
Parameter Type Direction Location Data Length Before
Executing the
Service
After Executing
the Service
nu1PointABase nu1 I Crypto
RAM
3*u2ModLength
+ 12
Input point A Resulting point A
in affine
coordinates
nu1Workspace nu1 I Crypto
RAM
4*u2ModLength
+ 48
– Workspace
43.3.6.7.5 Code Example
PUKCL_PARAM PUKCLParam;
PPUKCL_PARAM pvPUKCLParam = &PUKCLParam;
PUKCL (u2Option) = 0;
PUKCL _ZpEcConvProjToAffine(nu1ModBase) = <Base of the ram location of P>;
PUKCL _ZpEcConvProjToAffine(u2ModLength) = <Byte length of P>;
PUKCL _ZpEcConvProjToAffine(nu1CnsBase) = <Base of the ram location of Cns>;
PUKCL _ZpEcConvProjToAffine(nu1PointABase) = <Base of the ram location of the A point>;
PUKCL _ZpEcConvProjToAffine(nu1Workspace) = <Base of the ram location of the workspace>;
...
// vPUKCL_Process() is a macro command, which populates the service name
// and then calls the library...
vPUKCL_Process(ZpEcConvProjToAffine,&PUKCLParam);
if (PUKCL (u2Status) == PUKCL_OK)
{
...
}
else // Manage the error
43.3.6.7.6 Constraints
No overlapping between either input and output are allowed. The following conditions must be avoided to
ensure that the service works correctly:
• nu1ModBase, nu1CnsBase, nu1PointABase, nu1Workspace are not aligned on 32-bit boundaries
• {nu1ModBase, u2ModLength + 4}, {nu1CnsBase, u2ModLength + 8},{nu1PointABase,
3*u2ModLength+ 12}, {nu1Workspace, <WorkspaceLength>} are not in Crypto RAM
• u2ModLength is either: < 12, > 0xffc or not a 32-bit length
• All overlapping between {nu1ModBase, u2ModLength + 4}, {nu1CnsBase, u2ModLength +8},
{nu1PointABase, 3*u2ModLength + 12} and {nu1Workspace, 4*u2ModLength + 48}
43.3.6.7.7 Status Returned Values
Table 43-78. ZpEccConvAffineToProjective Service Return Codes
Returned Status Importance Meaning
PUKCL_OK – The computation passed without problem.
PUKCL_POINT_AT_INFINITY Warning The input point has its Z equal to zero, so it’s a
representation of the infinite point.
SAM D5x/E5x Family Data Sheet
Public Key Cryptography Controller (PUKCC)
© 2019 Microchip Technology Inc.
Datasheet
DS60001507E-page 1525