Datasheet

Table Of Contents

43.3.6.1.2 Points Representations

Depending on the representation (Projective or Affine), points are represented tn memory, as shown in

the following figure.

Figure 43-6. Points Representation in Memory

In this figure, the modulus is represented as a reference, and to show that coordinates are always to be

provided on the length of the modulus plus one 32-bit word.

The different types of representations are as follows:

Note:

1. The minimum value for u2ModLength is 12 bytes. Therefore, the significant length of the modulus

must be at least three 32-bit words.

2. In some cases the point can be the infinite point. In this case, it is represented with its Z

coordinates equal or congruent to zero.

43.3.6.1.3 Modulus and Modular Constant Parameters

In most of the services the following parameters must be provided:

• P the Modulus (often pointed by {nu1ModBase,u2ModLength + 4}): This parameter contains the

Modulus Integer prime P defining the Galois Field used in points coordinates computations. The

Modulus must be u2ModLength bytes long, while having a supplemental zeroed 32-bit word on the

MSB side.

SAM D5x/E5x Family Data Sheet

Public Key Cryptography Controller (PUKCC)

Datasheet

DS60001507E-page 1509