Elliptic Curve Cryptography. Elliptic curve cryptography makes use of elliptic curves in which the variables and coefficients are all restricted to elements of a finite field. Typically, elliptic curves are defined over either the integers modulo a prime number (GF(p)) or over binary polynomials (GF(2m)). An elliptic curve is a cubic equation of the form: y2 +axy + by = x3+ cx2 + dx + e. (1) where a, b, c, d, and e are real numbers. In an elliptic curve cryptosystem (ECC), the elliptic curve equation is defined as the form of Ep(a, b): y2 = x3+ax+b( mod p) (2) over a prime finite field Fp, where a, b ε Fp, p > 3, and 4a3 + 27b2 (mod p) ≠ 0. Generally, the security of ECC relies on the difficulties of the following problems [10]. Definition 1 Given two points P and Q over Ep(a, b), the elliptic curve discrete logarithm problem (ECDLP) is to find an integer s ε Fp* such that Q = s.P. Definition 2 Given three points P, s.P, and t.P over Ep(a, b) for s; t ε Fp*, the computational ▇▇▇▇▇▇-▇▇▇▇▇▇▇ problem (CDHP) is to find the point (s.t).P over Ep(a, b). Definition 3 Given two points P and Q = s.P + t.P over Ep(a, b) or s; t ε Fp*, the elliptic curve factorization problem (ECFP) is to find two points s. P and t.P over Ep(a, b). Up to now, there is no algorithm to be able to solve any of the above problems [10]
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Sources: Password Authenticated Key Agreement Scheme, Password Authenticated Key Agreement Scheme