org.cryptimeleon.math.structures.groups.lazy

Class LazyGroup

java.lang.Object

org.cryptimeleon.math.structures.groups.lazy.LazyGroup

All Implemented Interfaces:

RepresentationRestorer, Representable, StandaloneRepresentable, Group, Structure

public class LazyGroup
extends java.lang.Object
implements Group

A GroupImpl wrapper implementing deferred (lazy) evaluation for abelian groups with known finite order.

Allows for additional optimizations using information about the operations being applied. Specifically, multi-exponentiation techniques can be applied to significantly speed up computations.

For more information, see the documentation.

Constructor Summary

Constructors

Constructor and Description
LazyGroup(GroupImpl impl)
LazyGroup(GroupImpl impl, int exponentiationWindowSize, int precomputationWindowSize)
LazyGroup(Representation repr)
LazyGroup(Representation repr, int exponentiationWindowSize, int precomputationWindowSize)

Method Summary

Modifier and Type	Method and Description
GroupElementImpl	compute(GroupElementImpl base, java.math.BigInteger exponent, SmallExponentPrecomputation precomputation)
GroupElementImpl	compute(Multiexponentiation multiexp)
boolean	equals(java.lang.Object o)
int	getExponentiationWindowSize()
GroupElement	getGenerator() Returns any generator of this group if the group is cyclic and it's feasible to compute a generator.
GroupImpl	getImpl()
GroupElement	getNeutralElement() Returns the neutral element for this group
int	getPrecomputationWindowSize()
Representation	getRepresentation() The representation of this object.
ExpAlgorithm	getSelectedExpAlgorithm()
MultiExpAlgorithm	getSelectedMultiExpAlgorithm()
GroupElement	getUniformlyRandomElement() Returns an element of this structure that is drawn uniformly at random using a cryptographically strong RNG.
GroupElement	getUniformlyRandomNonNeutral() Generates a uniformly random non-neutral element of this group using a cryptographically strong RNG.
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.
Zn	getZn() Returns Zn, where n == size().
int	hashCode()
boolean	hasPrimeSize() Checks if the structure has prime size.
boolean	isCommutative() Returns true if this group is known to be commutative.
GroupElement	restoreElement(Representation repr) Creates an element of this structure from its representation.
void	setExponentiationWindowSize(int exponentiationWindowSize)
void	setPrecomputationWindowSize(int precomputationWindowSize)
void	setSelectedExpAlgorithm(ExpAlgorithm selectedExpAlgorithm)
void	setSelectedMultiExpAlgorithm(MultiExpAlgorithm selectedMultiExpAlgorithm)
java.math.BigInteger	size() Returns the number of elements in this structure (the size).
java.lang.String	toString()
protected LazyGroupElement	wrap(GroupElementImpl impl)

Methods inherited from class java.lang.Object

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

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

expr, getUniformlyRandomElements, getUniformlyRandomExponent, getUniformlyRandomExponents, getUniformlyRandomNonNeutrals, getUniformlyRandomNonzeroExponent, getUniformlyRandomNonzeroExponents, getUniformlyRandomUnitExponent, getUniformlyRandomUnitExponents, restoreFromRepresentation, restoreVector

Constructor Detail

LazyGroup

public LazyGroup(GroupImpl impl)

LazyGroup

public LazyGroup(GroupImpl impl,
                 int exponentiationWindowSize,
                 int precomputationWindowSize)

LazyGroup

public LazyGroup(Representation repr)

LazyGroup

public LazyGroup(Representation repr,
                 int exponentiationWindowSize,
                 int precomputationWindowSize)

Method Detail

wrap

protected LazyGroupElement wrap(GroupElementImpl impl)

getNeutralElement

public GroupElement getNeutralElement()

Description copied from interface: Group

Returns the neutral element for this group

Specified by:

getNeutralElement in interface Group

size

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

Description copied from interface: Structure

Returns the number of elements in this structure (the size).

Specified by:

size in interface Structure

Returns:

the number of elements contained in this structure or null if infinite

Throws:

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

hasPrimeSize

public boolean hasPrimeSize()

Description copied from interface: Structure

Checks if the structure has prime size.

Specified by:

hasPrimeSize in interface Structure

Returns:

true if the structure has prime size, else false.

getUniformlyRandomElement

public GroupElement getUniformlyRandomElement()
                                       throws java.lang.UnsupportedOperationException

Description copied from interface: Structure

Returns an element of this structure that is drawn uniformly at random using a cryptographically strong RNG.

Specified by:

getUniformlyRandomElement in interface Group

Specified by:

getUniformlyRandomElement in interface Structure

Throws:

java.lang.UnsupportedOperationException - if the operation is not supported

getUniformlyRandomNonNeutral

public GroupElement getUniformlyRandomNonNeutral()
                                          throws java.lang.UnsupportedOperationException

Description copied from interface: Group

Generates a uniformly random non-neutral element of this group using a cryptographically strong RNG.

Specified by:

getUniformlyRandomNonNeutral in interface Group

Throws:

java.lang.UnsupportedOperationException

restoreElement

public GroupElement restoreElement(Representation repr)

Description copied from interface: Structure

Creates an element of this structure from its representation.

Specified by:

restoreElement in interface Group

Specified by:

restoreElement in interface Structure

Parameters:

repr - the Representation returned by Representable.getRepresentation()

Returns:

the decoded element corresponding to the representation

getGenerator

public GroupElement getGenerator()
                          throws java.lang.UnsupportedOperationException

Description copied from interface: Group

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)!

Specified by:

getGenerator in interface Group

Throws:

java.lang.UnsupportedOperationException - if the group doesn't know or have a generator

getUniqueByteLength

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

Description copied from interface: Structure

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.

Specified by:

getUniqueByteLength in interface Structure

Returns:

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

isCommutative

public boolean isCommutative()

Description copied from interface: Group

Returns true if this group is known to be commutative.

Specified by:

isCommutative in interface Group

getZn

public Zn getZn()

Description copied from interface: Group

Returns Zn, where n == size().

Specified by:

getZn in interface Group

getRepresentation

public Representation getRepresentation()

Description copied from interface: Representable

The representation of this object. Used for serialization. A convenient way to implement this is using @link ReprUtil

Specified by:

getRepresentation in interface Representable

Returns:

a Representation or null if an equal object can be recreated without any information.

See Also:

Representation

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

compute

public GroupElementImpl compute(Multiexponentiation multiexp)

compute

public GroupElementImpl compute(GroupElementImpl base,
                                java.math.BigInteger exponent,
                                SmallExponentPrecomputation precomputation)

getExponentiationWindowSize

public int getExponentiationWindowSize()

setExponentiationWindowSize

public void setExponentiationWindowSize(int exponentiationWindowSize)

getPrecomputationWindowSize

public int getPrecomputationWindowSize()

setPrecomputationWindowSize

public void setPrecomputationWindowSize(int precomputationWindowSize)

getSelectedMultiExpAlgorithm

public MultiExpAlgorithm getSelectedMultiExpAlgorithm()

setSelectedMultiExpAlgorithm

public void setSelectedMultiExpAlgorithm(MultiExpAlgorithm selectedMultiExpAlgorithm)

getSelectedExpAlgorithm

public ExpAlgorithm getSelectedExpAlgorithm()

setSelectedExpAlgorithm

public void setSelectedExpAlgorithm(ExpAlgorithm selectedExpAlgorithm)

getImpl

public GroupImpl getImpl()