Package org.bouncycastle.math.ec

## Class ECCurve.AbstractF2m

- java.lang.Object
- - org.bouncycastle.math.ec.ECCurve
  - - org.bouncycastle.math.ec.ECCurve.AbstractF2m

- Direct Known Subclasses:
    `ECCurve.F2m`, `SecT113R1Curve`, `SecT113R2Curve`, `SecT131R1Curve`, `SecT131R2Curve`, `SecT163K1Curve`, `SecT163R1Curve`, `SecT163R2Curve`, `SecT193R1Curve`, `SecT193R2Curve`, `SecT233K1Curve`, `SecT233R1Curve`, `SecT239K1Curve`, `SecT283K1Curve`, `SecT283R1Curve`, `SecT409K1Curve`, `SecT409R1Curve`, `SecT571K1Curve`, `SecT571R1Curve`
  Enclosing class:
    ECCurve

      public abstract static class ECCurve.AbstractF2m
      extends ECCurve

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class org.bouncycastle.math.ec.ECCurve

      `ECCurve.AbstractF2m, ECCurve.AbstractFp, ECCurve.Config, ECCurve.F2m, ECCurve.Fp`

  - ### Field Summary

    - ### Fields inherited from class org.bouncycastle.math.ec.ECCurve

      `a, b, cofactor, coord, COORD_AFFINE, COORD_HOMOGENEOUS, COORD_JACOBIAN, COORD_JACOBIAN_CHUDNOVSKY, COORD_JACOBIAN_MODIFIED, COORD_LAMBDA_AFFINE, COORD_LAMBDA_PROJECTIVE, COORD_SKEWED, endomorphism, field, multiplier, order`

  - ### Constructor Summary

    Constructors
    Modifier | Constructor | Description
    --- | --- | ---
    `protected` | `AbstractF2m​(int m, int k1, int k2, int k3)` |

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `ECPoint` | `createPoint​(java.math.BigInteger x, java.math.BigInteger y)` |
    `protected ECPoint` | `decompressPoint​(int yTilde, java.math.BigInteger X1)` | Decompresses a compressed point P = (xp, yp) (X9.62 s 4.2.2).
    `static java.math.BigInteger` | `inverse​(int m, int[] ks, java.math.BigInteger x)` |
    `boolean` | `isKoblitz()` | Returns true if this is a Koblitz curve (ABC curve).
    `boolean` | `isValidFieldElement​(java.math.BigInteger x)` |
    `ECFieldElement` | `randomFieldElement​(java.security.SecureRandom r)` |
    `ECFieldElement` | `randomFieldElementMult​(java.security.SecureRandom r)` |
    `protected ECFieldElement` | `solveQuadraticEquation​(ECFieldElement beta)` | Solves a quadratic equation `z2 + z = beta`(X9.62 D.1.6) The other solution is `z + 1`.

    - ### Methods inherited from class org.bouncycastle.math.ec.ECCurve

      `checkPoint, checkPoints, checkPoints, cloneCurve, configure, createCacheSafeLookupTable, createDefaultMultiplier, createRawPoint, createRawPoint, decodePoint, equals, equals, fromBigInteger, getA, getAllCoordinateSystems, getB, getCofactor, getCoordinateSystem, getEndomorphism, getField, getFieldSize, getInfinity, getMultiplier, getOrder, getPreCompInfo, hashCode, importPoint, normalizeAll, normalizeAll, precompute, supportsCoordinateSystem, validatePoint`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### AbstractF2m

          protected AbstractF2m​(int m,
                                int k1,
                                int k2,
                                int k3)

  - ### Method Detail

    - #### inverse

          public static java.math.BigInteger inverse​(int m,
                                                     int[] ks,
                                                     java.math.BigInteger x)

    - #### createPoint

          public ECPoint createPoint​(java.math.BigInteger x,
                                     java.math.BigInteger y)

      Overrides:
        `createPoint` in class `ECCurve`

    - #### isValidFieldElement

          public boolean isValidFieldElement​(java.math.BigInteger x)

      Specified by:
        `isValidFieldElement` in class `ECCurve`

    - #### randomFieldElement

          public ECFieldElement randomFieldElement​(java.security.SecureRandom r)

      Specified by:
        `randomFieldElement` in class `ECCurve`

    - #### randomFieldElementMult

          public ECFieldElement randomFieldElementMult​(java.security.SecureRandom r)

      Specified by:
        `randomFieldElementMult` in class `ECCurve`

    - #### decompressPoint

          protected ECPoint decompressPoint​(int yTilde,
                                            java.math.BigInteger X1)

      Decompresses a compressed point P = (xp, yp) (X9.62 s 4.2.2).
      Specified by:
        `decompressPoint` in class `ECCurve`
      Parameters:
        `yTilde` - ~yp, an indication bit for the decompression of yp.
        `X1` - The field element xp.
      Returns:
        the decompressed point.

    - #### solveQuadraticEquation

          protected ECFieldElement solveQuadraticEquation​(ECFieldElement beta)

      Solves a quadratic equation `z2 + z = beta`(X9.62 D.1.6) The other solution is `z + 1`.
      Parameters:
        `beta` - The value to solve the quadratic equation for.
      Returns:
        the solution for `z2 + z = beta` or `null` if no solution exists.

    - #### isKoblitz

          public boolean isKoblitz()

      Returns true if this is a Koblitz curve (ABC curve).
      Returns:
        true if this is a Koblitz curve (ABC curve), false otherwise