XIP4001C from Xiphera is a very compact Intellectual Property (IP) core designed for efficient key exchange using the X25519 protocol. XIP4001C implements arithmetic on Curve25519 , and provides a security level of 128 bits. Curve25519 is used in numerous contemporary security protocols and applications, including TLS 1.3.
XIP4001C has been designed for easy integration with FPGA- and ASIC-based designs in a vendor-agnostic design methodology, and the functionality of XIP4001C does not rely on any FPGA manufacturer-specific features.
XIP4001C calculates the operation Qₓ = sPₓ using the Montgomery Ladder Algorithm, where
The internal word width as well as the bus widths for din and dout is set to 17 bits, as this leads to an efficient internal implementation  of the multiplication algorithm.
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Figure 1: Internal high-level block diagram of XIP4001C
 Curve25519 is formally defined as y² = x³ + 486662x² + x over the finite field defined by the prime number 2²⁵⁵ − 19.
 The exact number depends on the targeted FPGA architecture.
 15 · 17 bits = 255 bits.
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