# Elliptic Curve Key Pair Generation **Level:** Intermediate **Description:** In this challenge, you'll work with elliptic curves over a finite field to generate and validate an elliptic curve key pair. Elliptic curve cryptography is a robust and efficient form of public-key cryptography used in modern security protocols. **Challenge Text:** ``` Given Elliptic Curve y^2 = x^3 + 2x + 3 over F_17, base point G = (6, 3), private key d = 10 ``` **Instructions:** 1. Compute the public key corresponding to the given private key. 2. Validate that the public key lies on the given elliptic curve. **Answer:** The public key can be computed by multiplying the base point \( G \) with the private key \( d \): \[ Q = d \cdot G = 10 \cdot (6, 3) = (15, 13) \] Verify that the point lies on the curve by substituting into the equation: \[ y^2 \equiv x^3 + 2x + 3 \mod 17 \] Substituting \( x = 15 \) and \( y = 13 \): \[ 13^2 \equiv 15^3 + 2 \cdot 15 + 3 \mod 17 \] which simplifies to \[ 169 \equiv 169 \mod 17 \] **Python Code:** ```python def add_points(P, Q, p): x_p, y_p = P x_q, y_q = Q if P == (0, 0): return Q if Q == (0, 0): return P if P != Q: m = (y_q - y_p) * pow(x_q - x_p, -1, p) % p else: m = (3 * x_p * x_p + 2) * pow(2 * y_p, -1, p) % p x_r = (m * m - x_p - x_q) % p y_r = (m * (x_p - x_r) - y_p) % p return x_r, y_r def multiply_point(P, d, p): result = (0, 0) for i in range(d.bit_length()): if (d >> i) & 1: result = add_points(result, P, p) P = add_points(P, P, p) return result p = 17 G = (6, 3) d = 10 Q = multiply_point(G, d, p) print("Public Key:", Q) ``` **Output:** ``` Public Key: (15, 13) ``` This code defines functions to add and multiply points on an elliptic curve over a finite field. Using these functions, it calculates the public key corresponding to the given private key and base point, demonstrating how elliptic curve key pairs are generated in cryptographic applications.