Package net.i2p.crypto.eddsa.math

Class Encoding

java.lang.Object
net.i2p.crypto.eddsa.math.Encoding
All Implemented Interfaces:
Serializable
Direct Known Subclasses:
BigIntegerLittleEndianEncoding, Ed25519LittleEndianEncoding
public abstract class Encoding
extends Object
implements Serializable
Common interface for all $(b-1)$-bit encodings of elements of EdDSA finite fields.
Since:
0.9.15
Author:
str4d
See Also:
Serialized Form

  • Field Details

  • Constructor Details

  • Method Details

    • setField

      public void setField​(Field f)

    • 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.

    • 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'.

    • 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