Field Detail

• f

  protected Field f

  The field

Constructor Detail

• Encoding

  public Encoding()

Method Detail

• decode

  public abstract FieldElement decode(byte[] in)

  Decode a FieldElement from its $(b-1)$-bit encoding. The highest bit is masked out.

  Parameters:

  in - the $(b-1)$-bit encoding of a FieldElement.

  Returns:

  the FieldElement represented by 'val'.

• encode

  public abstract byte[] encode(FieldElement x)

  Encode a FieldElement in its $(b-1)$-bit encoding.

  Parameters:

  x - the FieldElement to encode

  Returns:

  the $(b-1)$-bit encoding of this FieldElement.

• isNegative

  public abstract boolean isNegative(FieldElement x)

  From the Ed25519 paper:
  $x$ is negative if the $(b-1)$-bit encoding of $x$ is lexicographically larger than the $(b-1)$-bit encoding of -x. If $q$ is an odd prime and the encoding is the little-endian representation of $\{0, 1,\dots, q-1\}$ then the negative elements of $F_q$ are $\{1, 3, 5,\dots, q-2\}$.

  Parameters:

  x - the FieldElement to check

  Returns:

  true if negative

• setField

  public void setField(Field f)

  Set the field.

  Parameters:

  f - the field to set