org.cryptimeleon.math.structures.groups

Class RingUnitGroupImpl

java.lang.Object

org.cryptimeleon.math.structures.groups.RingGroupImpl

org.cryptimeleon.math.structures.groups.RingUnitGroupImpl

All Implemented Interfaces:

RepresentationRestorer, Representable, StandaloneRepresentable, GroupImpl

public class RingUnitGroupImpl
extends RingGroupImpl

Allows interpreting a ring as its unit group.

The unit group consists of the set of elements with a multiplicative inverse. The group operation is multiplication and the neutral element is called the one element.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	RingUnitGroupImpl.RingUnitGroupElementImpl A ring element interpreted as an element of the ring's unit group.

Nested classes/interfaces inherited from class org.cryptimeleon.math.structures.groups.RingGroupImpl

RingGroupImpl.RingGroupElementImpl

Field Summary

Fields inherited from class org.cryptimeleon.math.structures.groups.RingGroupImpl

ring

Constructor Summary

Constructors

Constructor and Description
RingUnitGroupImpl(Representation repr)
RingUnitGroupImpl(Ring ring)

Method Summary

Modifier and Type	Method and Description
double	estimateCostInvPerOp() Estimates the number of inversions that can be done per group operation for the same cost.
RingGroupImpl.RingGroupElementImpl	getElement(RingElement ringElement) Creates an element of this group from the given ring element.
GroupElementImpl	getGenerator() Returns any generator of this group if the group is cyclic and it's feasible to compute a generator.
RingUnitGroupImpl.RingUnitGroupElementImpl	getNeutralElement() Returns the neutral element of this group.
RingUnitGroupImpl.RingUnitGroupElementImpl	getUniformlyRandomElement() Generates a uniformly random element of this group.
java.util.Optional<java.lang.Integer>	getUniqueByteLength() Returns the number of bytes returned by this structure's UniqueByteRepresentable.getUniqueByteRepresentation(), or an empty Optional if this structure's elements do not guarantee a fixed length.
boolean	hasPrimeSize() Returns true if the size of this structure is known and prime.
boolean	isCommutative() Returns true if this group is known to be commutative.
RingUnitGroupImpl.RingUnitGroupElementImpl	restoreElement(Representation repr) Restores a group element from its representation.
java.math.BigInteger	size() Retrieves number of elements in the group if possible.

Methods inherited from class org.cryptimeleon.math.structures.groups.RingGroupImpl

equals, getRepresentation, getRing, hashCode, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.cryptimeleon.math.structures.groups.GroupImpl

exp, getUniformlyRandomNonNeutral, implementsOwnExp, implementsOwnMultiExp, multiexp, restoreFromRepresentation

Constructor Detail

RingUnitGroupImpl

public RingUnitGroupImpl(Ring ring)

RingUnitGroupImpl

public RingUnitGroupImpl(Representation repr)

Method Detail

getElement

public RingGroupImpl.RingGroupElementImpl getElement(RingElement ringElement)

Description copied from class: RingGroupImpl

Creates an element of this group from the given ring element.

Specified by:

getElement in class RingGroupImpl

Parameters:

ringElement - the ring element to convert

Returns:

the given ring element as an element of this group

size

public java.math.BigInteger size()
                          throws java.lang.UnsupportedOperationException

Description copied from interface: GroupImpl

Retrieves number of elements in the group if possible.

Returns:

size of this group (number of group elements in it) or null if infinite

Throws:

java.lang.UnsupportedOperationException - if the number of elements is unknown or is too expensive to compute

hasPrimeSize

public boolean hasPrimeSize()

Description copied from interface: GroupImpl

Returns true if the size of this structure is known and prime.

estimateCostInvPerOp

public double estimateCostInvPerOp()

Description copied from interface: GroupImpl

Estimates the number of inversions that can be done per group operation for the same cost. For example, 2 would mean that an inversion costs half as much as a group operation, on average.

Returns:

Estimated number of inversions that can be done per group operation for the same cost

getNeutralElement

public RingUnitGroupImpl.RingUnitGroupElementImpl getNeutralElement()

Description copied from interface: GroupImpl

Returns the neutral element of this group.

getUniformlyRandomElement

public RingUnitGroupImpl.RingUnitGroupElementImpl getUniformlyRandomElement()
                                                                     throws java.lang.UnsupportedOperationException

Description copied from interface: GroupImpl

Generates a uniformly random element of this group.

Throws:

java.lang.UnsupportedOperationException - if the random generation cannot be done

restoreElement

public RingUnitGroupImpl.RingUnitGroupElementImpl restoreElement(Representation repr)

Description copied from interface: GroupImpl

Restores a group element from its representation.

getGenerator

public GroupElementImpl getGenerator()
                              throws java.lang.UnsupportedOperationException

Description copied from interface: GroupImpl

Returns any generator of this group if the group is cyclic and it's feasible to compute a generator.

Repeated calls may or may not always supply the same generator again (i.e. the output is not guaranteed to be random)!

Throws:

java.lang.UnsupportedOperationException - if group is not cyclic or it's too hard to compute a generator

getUniqueByteLength

public java.util.Optional<java.lang.Integer> getUniqueByteLength()

Description copied from interface: GroupImpl

Returns the number of bytes returned by this structure's UniqueByteRepresentable.getUniqueByteRepresentation(), or an empty Optional if this structure's elements do not guarantee a fixed length.

For example, elements of Zp will always be represented by ceil(ceil(log(p))/8) bytes, hence getUniqueByteLength() would return ceil(ceil(log(p))/8).

A polynomial ring would return an empty Optional since a polynomial's unique byte representation length depends on its degree.

Returns:

the guaranteed fixed length of getUniqueByteRepresentation(), or an empty Optional, if no guarantee

isCommutative

public boolean isCommutative()

Description copied from interface: GroupImpl

Returns true if this group is known to be commutative.