net.i2p.crypto.eddsa.math.bigint

Class BigIntegerLittleEndianEncoding

java.lang.Object

net.i2p.crypto.eddsa.math.Encoding

net.i2p.crypto.eddsa.math.bigint.BigIntegerLittleEndianEncoding

All Implemented Interfaces:

Serializable

public class BigIntegerLittleEndianEncoding
extends Encoding
implements Serializable

See Also:

Serialized Form

Field Summary

Fields inherited from class net.i2p.crypto.eddsa.math.Encoding

f

Constructor Summary

Constructors

Constructor and Description
BigIntegerLittleEndianEncoding()

Method Summary

Methods

Modifier and Type	Method and Description
FieldElement	decode(byte[] in) Decode a FieldElement from its (b-1)-bit encoding.
byte[]	encode(BigInteger x) Convert x to little endian.
byte[]	encode(FieldElement x) Encode a FieldElement in its (b-1)-bit encoding.
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.
void	setField(Field f)
BigInteger	toBigInteger(byte[] in) Convert in to big endian

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BigIntegerLittleEndianEncoding

public BigIntegerLittleEndianEncoding()

Method Detail

setField

public void setField(Field f)

Overrides:

setField in class Encoding

encode

public byte[] encode(FieldElement x)

Description copied from class: Encoding

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

Specified by:

encode in class Encoding

Returns:

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

encode

public byte[] encode(BigInteger x)

Convert x to little endian. Constant time.

Returns:

array of length b/8

decode

public FieldElement decode(byte[] in)

Description copied from class: Encoding

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

Specified by:

decode in class Encoding

Parameters:

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

Returns:

the FieldElement represented by 'val'.

toBigInteger

public BigInteger toBigInteger(byte[] in)

Convert in to big endian

isNegative

public 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,..., q-1} then the negative elements of F_q are {1, 3, 5,..., q-2}.

Specified by:

isNegative in class Encoding

Returns:

true if negative