cha2 curve check
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@ -56,18 +56,36 @@ impl EllipticCurve {
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F(X, Y) = Y² - X³ - {a}X - {b}")
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}
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// check diskriminante
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let d = 4*a.pow(3) + 27*b.pow(2);
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if field.reduce::<_, u128>(d) == 0 {
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if verbose {
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println!("4*{a}³ + 27*{b}² = {d} = {} != 0\n\
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Check for Diskriminante not passed", field.reduce::<_, u128>(d));
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// check if the curve is valid
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if field.cha > 2 {
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let d = 4*a.pow(3) + 27*b.pow(2);
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if field.reduce::<_, u128>(d) == 0 {
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if verbose {
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println!("4*{a}³ + 27*{b}² = {d} = {} != 0\n\
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Check for Diskriminante not passed", field.reduce::<_, u128>(d));
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}
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return Err(String::from("Diskriminante not 0"));
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}
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else if verbose {
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println!("4*{a}³ + 27*{b}² = {d} = {} != 0\n\
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Check for Diskriminante passed", field.reduce::<_, u128>(d));
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}
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return Err(String::from("Diskriminante not 0"));
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}
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else if verbose {
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println!("4*{a}³ + 27*{b}² = {d} = {} != 0\n\
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Check for Diskriminante passed", field.reduce::<_, u128>(d));
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else {
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let valid: bool = field.reduce::<_, i128>(b) == 0;
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if verbose {
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if valid {
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println!("b = {b} != 0 => Curve valid");
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}
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else {
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println!("b = {b} == 0 => Curve invalid")
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}
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}
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if !valid {
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return Err(String::from("b == 0 => Curve invalid"));
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}
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}
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let mut infty = EllipticCurvePoint::new(0, 0);
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@ -121,7 +139,9 @@ impl EllipticCurve {
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pub fn check_point(&self, p: EllipticCurvePoint, verbose: bool) -> bool {
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if p.is_infinity_point {
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println!("p is infinity: {p}");
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if self.verbose {
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println!("p is infinity: {p}");
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}
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return true;
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}
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let mut valid = true;
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@ -310,8 +330,11 @@ impl EllipticCurve {
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/// get negative of a point
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pub fn neg(&self, p: EllipticCurvePoint) -> EllipticCurvePoint {
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self.new_point(p.r, self.field.reduce::<_, u128>(-(p.s as i128))).expect("negation of \
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point is not on field, math error")
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if p.is_infinity_point {
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return p;
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}
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self.new_point(p.r, self.field.reduce(-(p.s as i128))).expect(format!("negation of \
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point is not on field, math error: {}", p).as_str())
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}
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/// multip.s a point by an integer
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@ -327,7 +350,7 @@ impl EllipticCurve {
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}
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let t: usize = num::cast(t).unwrap();
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if t < 1 {
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return Err(String::from("point multiplication works only if t > 0"));
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return Ok(self.INFINITY_POINT);
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}
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if self.verbose {
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println!("h = t * g = {t} * {g}\n\
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@ -453,7 +476,18 @@ impl EllipticCurve {
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impl std::fmt::Display for EllipticCurve{
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fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
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write!(f, "F(X, Y) = Y² - X³ -{}X - {}", self.a, self.b)
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if self.field.prime_base {
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write!(f, "F(X, Y) = Y² - X³ -{}X - {}", self.a, self.b)
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}
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else if self.field.cha == 2 {
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write!(f, "F(X, Y) = Y² + XY + X³ + ({}) * X² + ({})",
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self.field.display(self.a),
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self.field.display(self.b),
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)
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}
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else {
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write!(f, "ERROR")
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}
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}
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}
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