43.3.3.3 Parameter Passing (Special Considerations)

Most of the PUKCL services work with memory area and accept pointers and lengths as parameters to define input and output areas. Most of the time, the pointers and lengths are untouched by the services, while the defined areas are read, filled, or overwritten. These memory areas are defined with an initial pointer and a byte length. For most of the commands, the memory area location must be in the PUKCC Cryptographic RAM. The Cryptographic RAM is the memory area for parameter exchange with the PUKCL and is 4 Kbytes large. Sometimes memory areas can be located in Embedded SRAM, which is detailed in the Location column of the parameters description tables.

When working with binary fields, polynomials in GF(2n) need no transformation to be written in an area:
  • Each bit represents a polynomial coefficient 0 or 1
  • The polynomials must be written Low Significant Byte First
  • A zero padding on the Most Significant Bytes may be added if the area is larger than the real size of the polynomial
Important: The Cryptographic RAM is 4 Kbytes in size and is dedicated to PUKCC. However, to ensure correct library operation, the two last 32-bit words must not be used. Unless otherwise specified, these memory areas contain integers in GF(p) or polynomials in GF(2n) with the Less Significant Byte first.

Unless otherwise specified, the length must be a multiple of four and the pointers must be four bytes aligned. This is because most of the services work with 32-bit words.