org.cryptimeleon.craco.sig.hashthensign

Class HashThenSign

java.lang.Object

org.cryptimeleon.craco.sig.hashthensign.HashThenSign

All Implemented Interfaces:

SignatureScheme, org.cryptimeleon.math.serialization.annotations.RepresentationRestorer, org.cryptimeleon.math.serialization.Representable, org.cryptimeleon.math.serialization.StandaloneRepresentable

public class HashThenSign
extends java.lang.Object
implements SignatureScheme

Simple implementation of the hash-then-sign paradigm, where the given hash function will be used to hash the plaintext before verifying it with the signature scheme.

Constructor Summary

Constructors

Constructor and Description
HashThenSign(org.cryptimeleon.math.hash.HashFunction hashFunction, SignatureScheme signatureScheme)
HashThenSign(org.cryptimeleon.math.serialization.Representation repr)
HashThenSign(SignatureScheme signatureScheme) This constructor instantiates the Hash-then-Sign construction with a suitable hash function for the given signature scheme.

Method Summary

Modifier and Type	Method and Description
boolean	equals(java.lang.Object obj)
int	getMaxNumberOfBytesForMapToPlaintext() Returns the maximal number of bytes that can be mapped injectively to a PlainText by SignatureScheme.mapToPlaintext(byte[], SigningKey) and SignatureScheme.mapToPlaintext(byte[], VerificationKey).
org.cryptimeleon.math.serialization.Representation	getRepresentation()
int	hashCode()
PlainText	mapToPlaintext(byte[] bytes, SigningKey sk) Provides an injective mapping of the given bytes to a PlainText usable with this scheme (which may be a MessageBlock).
PlainText	mapToPlaintext(byte[] bytes, VerificationKey pk) Provides an injective mapping of the given bytes to a PlainText usable with this scheme (which may be a MessageBlock).
PlainText	restorePlainText(org.cryptimeleon.math.serialization.Representation repr)
Signature	restoreSignature(org.cryptimeleon.math.serialization.Representation repr)
SigningKey	restoreSigningKey(org.cryptimeleon.math.serialization.Representation repr)
VerificationKey	restoreVerificationKey(org.cryptimeleon.math.serialization.Representation repr)
Signature	sign(org.cryptimeleon.math.hash.ByteAccumulator plaintextBytes, SigningKey secretKey)
Signature	sign(PlainText plainText, SigningKey secretKey) Signs the giving plaintext using the given signing key.
java.lang.Boolean	verify(org.cryptimeleon.math.hash.ByteAccumulator plaintextBytes, Signature signature, VerificationKey publicKey)
java.lang.Boolean	verify(PlainText plainText, Signature signature, VerificationKey publicKey) Verifies the given signature for the given plaintext using the given verification key.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.cryptimeleon.craco.sig.SignatureScheme

restoreFromRepresentation, sign, verify

Constructor Detail

HashThenSign

public HashThenSign(org.cryptimeleon.math.hash.HashFunction hashFunction,
                    SignatureScheme signatureScheme)

HashThenSign

public HashThenSign(SignatureScheme signatureScheme)

This constructor instantiates the Hash-then-Sign construction with a suitable hash function for the given signature scheme. The default hash function used here is VariableOutputLengthHashFunction.

HashThenSign

public HashThenSign(org.cryptimeleon.math.serialization.Representation repr)

Method Detail

getRepresentation

public org.cryptimeleon.math.serialization.Representation getRepresentation()

Specified by:

getRepresentation in interface org.cryptimeleon.math.serialization.Representable

sign

public Signature sign(org.cryptimeleon.math.hash.ByteAccumulator plaintextBytes,
                      SigningKey secretKey)

sign

public Signature sign(PlainText plainText,
                      SigningKey secretKey)

Description copied from interface: SignatureScheme

Signs the giving plaintext using the given signing key. The signing key should contain all information necessary to sign, therefore public key is not needed.

Specified by:

sign in interface SignatureScheme

Parameters:

plainText - the message to sign

secretKey - the secret signing key

Returns:

signature on plainText computed using secretKey

verify

public java.lang.Boolean verify(org.cryptimeleon.math.hash.ByteAccumulator plaintextBytes,
                                Signature signature,
                                VerificationKey publicKey)

verify

public java.lang.Boolean verify(PlainText plainText,
                                Signature signature,
                                VerificationKey publicKey)

Description copied from interface: SignatureScheme

Verifies the given signature for the given plaintext using the given verification key.

Specified by:

verify in interface SignatureScheme

Parameters:

plainText - the plaintext the signature should validate against

signature - the signature to verify

publicKey - the verification key to verify with

Returns:

true if verification succeeds, false else

restorePlainText

public PlainText restorePlainText(org.cryptimeleon.math.serialization.Representation repr)

Specified by:

restorePlainText in interface SignatureScheme

restoreSignature

public Signature restoreSignature(org.cryptimeleon.math.serialization.Representation repr)

Specified by:

restoreSignature in interface SignatureScheme

restoreSigningKey

public SigningKey restoreSigningKey(org.cryptimeleon.math.serialization.Representation repr)

Specified by:

restoreSigningKey in interface SignatureScheme

restoreVerificationKey

public VerificationKey restoreVerificationKey(org.cryptimeleon.math.serialization.Representation repr)

Specified by:

restoreVerificationKey in interface SignatureScheme

mapToPlaintext

public PlainText mapToPlaintext(byte[] bytes,
                                VerificationKey pk)

Description copied from interface: SignatureScheme

Provides an injective mapping of the given bytes to a PlainText usable with this scheme (which may be a MessageBlock).

It only guarantees injectivity for arrays of the same length. Applications that would like to use mapToPlaintext with multiple different array lengths may want to devise a padding method and then only call mapToPlaintext with byte arrays of the same (padded) length.

The contract is that VerificationKey pk and SigningKey sk are compatible (in the sense that verify(m,sign(m, sk),pk) == true), then mapToPlaintext(bytes, pk)) equals mapToPlaintext(bytes, sk) for all bytes.

Specified by:

mapToPlaintext in interface SignatureScheme

Parameters:

bytes - bytes to be mapped to a PlainText

pk - the verification key for which the resulting PlainText should be valid (note that the plaintext space may differ for different verification keys).

Returns:

the corresponding plaintext

mapToPlaintext

public PlainText mapToPlaintext(byte[] bytes,
                                SigningKey sk)

Description copied from interface: SignatureScheme

Provides an injective mapping of the given bytes to a PlainText usable with this scheme (which may be a MessageBlock).

It only guarantees injectivity for arrays of the same length. Applications that would like to use mapToPlaintext with multiple different array lengths may want to devise a padding method and then only call mapToPlaintext with byte arrays of the same (padded) length.

The contract is that VerificationKey pk and SigningKey sk are compatible (in the sense that verify(m,sign(m, sk),pk) == true), then mapToPlaintext(bytes, pk)) equals mapToPlaintext(bytes, sk) for all bytes.

Specified by:

mapToPlaintext in interface SignatureScheme

Parameters:

bytes - bytes to be mapped to a PlainText

sk - the signing key for which the resulting PlainText should be valid (note that the plaintext space may differ for different signing keys).

Returns:

the corresponding plaintext

getMaxNumberOfBytesForMapToPlaintext

public int getMaxNumberOfBytesForMapToPlaintext()

Description copied from interface: SignatureScheme

Returns the maximal number of bytes that can be mapped injectively to a PlainText by SignatureScheme.mapToPlaintext(byte[], SigningKey) and SignatureScheme.mapToPlaintext(byte[], VerificationKey).

As described in SignatureScheme.mapToPlaintext(byte[], org.cryptimeleon.craco.sig.VerificationKey) there might be no injective PlainText for some byte arrays, e.g. if the byte array is too long. Therefore, this method provides the maximal number of bytes that can be mapped injectively to a PlainText.

Specified by:

getMaxNumberOfBytesForMapToPlaintext in interface SignatureScheme

Returns:

maximal number of bytes that can be given to SignatureScheme.mapToPlaintext(byte[], org.cryptimeleon.craco.sig.VerificationKey).

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object