iaik.ixsil.algorithms

Class SignatureAlgorithmImplDSA

java.lang.Object

iaik.ixsil.algorithms.Algorithm

iaik.ixsil.algorithms.SignatureAlgorithm

iaik.ixsil.algorithms.SignatureAlgorithmImplDSA

public class SignatureAlgorithmImplDSA
extends SignatureAlgorithm

Provides an signature algorithm implementation of the DSA signature algorithm, as it has been specified in XML Signature, Signature Algorithms. The Java Cryptography Architecture API is used for implementing the cryptographic computations.

Field Summary

Fields

Modifier and Type	Field and Description
protected static java.lang.String	DEFAULT_ALGORITHM_URI_ The default algorithm URI for this algorithm implementation.
protected static java.lang.String	DSA_JCA_ALGID_ The identifier used for the DSA algorithm within the Java Cryptography Architecture.
protected java.security.interfaces.DSAPublicKey	publicKey_ The public key used to verify the signature.

Fields inherited from class iaik.ixsil.algorithms.SignatureAlgorithm

input_, jCEProviderName_, privateKey_

Fields inherited from class iaik.ixsil.algorithms.Algorithm

uri_

Constructor Summary

Constructors

Constructor and Description
SignatureAlgorithmImplDSA() Standard constructor.

Method Summary

Modifier and Type	Method and Description
protected byte[]	removeSignumAndAlign20(byte[] signedInteger) Receives the byte representation of a POSITIVE integer value as two's-complement representation.
void	setSignerKey(java.security.interfaces.DSAPrivateKey signerKey) Sets the private key, which is used to compute the signature for the algorithm's input.
void	setVerifierKey(java.security.Key verifierKey) Sets the public key, which is used to verify the signature for the algorithm's input.
java.io.InputStream	sign() Computes the signature value for the input previously provided by means of method SignatureAlgorithm.setInput(java.io.InputStream).
org.w3c.dom.Element	toElement(org.w3c.dom.Document signatureDOMDoc) Returns the DOM element representation of the algorithm.
boolean	verifierKeyUnknown() Gets the information, if this signature algorithm knows about the verification key.
boolean	verify(java.io.InputStream signature) Verifies the specified signature for the input data previously set with method SignatureAlgorithm.setInput(java.io.InputStream).

Methods inherited from class iaik.ixsil.algorithms.SignatureAlgorithm

setInput, setJCEProviderName, setSignerKey

Methods inherited from class iaik.ixsil.algorithms.Algorithm

getURI, setParameters, setURI

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_ALGORITHM_URI_

protected static final java.lang.String DEFAULT_ALGORITHM_URI_

The default algorithm URI for this algorithm implementation.

See Also:

Constant Field Values

DSA_JCA_ALGID_

protected static final java.lang.String DSA_JCA_ALGID_

The identifier used for the DSA algorithm within the Java Cryptography Architecture.

See Also:

Constant Field Values

publicKey_

protected java.security.interfaces.DSAPublicKey publicKey_

The public key used to verify the signature.

Constructor Detail

SignatureAlgorithmImplDSA

public SignatureAlgorithmImplDSA()

Standard constructor. Sets the default value for the algorithm URI to http://www.w3.org/2000/09/xmldsig#dsa-sha1.

Method Detail

toElement

public org.w3c.dom.Element toElement(org.w3c.dom.Document signatureDOMDoc)
                              throws AlgorithmException

Returns the DOM element representation of the algorithm.

Specified by:

toElement in class Algorithm

Parameters:

signatureDOMDoc - The DOM document which should be used to create necessary DOM nodes. Must not be null.

Returns:

the DOM element representation of the algorithm.

Throws:

AlgorithmException - if no identifying URI has been specified for this algorithm.

sign

public java.io.InputStream sign()
                         throws AlgorithmException

Computes the signature value for the input previously provided by means of method SignatureAlgorithm.setInput(java.io.InputStream).

Specified by:

sign in class SignatureAlgorithm

Returns:

the signature value for the input specified with method SignatureAlgorithm.setInput(java.io.InputStream). This value will NOT be base64 encoded.

Throws:

AlgorithmException - if the signer key or the input data have not been set, or if computing the signature value fails for any reason.

verify

public boolean verify(java.io.InputStream signature)
               throws AlgorithmException

Verifies the specified signature for the input data previously set with method SignatureAlgorithm.setInput(java.io.InputStream).

Specified by:

verify in class SignatureAlgorithm

Parameters:

signature - The bytes representing the signature to be verified. Must not be null.

Returns:

true, if the signature is valid, false otherwise.

Throws:

AlgorithmException - if the verifier key or the input data have not been set, or if the signature does not consist of exactly 40 bytes, or if verifying the signature fails for any reason.

setSignerKey

public void setSignerKey(java.security.interfaces.DSAPrivateKey signerKey)

Sets the private key, which is used to compute the signature for the algorithm's input.

Parameters:

signerKey - The private key for computing the signature. Must not be null.

setVerifierKey

public void setVerifierKey(java.security.Key verifierKey)
                    throws AlgorithmException

Sets the public key, which is used to verify the signature for the algorithm's input.

Specified by:

setVerifierKey in class SignatureAlgorithm

Parameters:

verifierKey - The public key for verifying the signature. Must be an instance of DSAPublicKey and must not be null.

Throws:

AlgorithmException - if the specified key is not an instance of DSAPublicKey.

verifierKeyUnknown

public boolean verifierKeyUnknown()

Gets the information, if this signature algorithm knows about the verification key. This depends on wheter the key has already been set explicitely with method setVerifierKey(java.security.Key) or not.

Specified by:

verifierKeyUnknown in class SignatureAlgorithm

Returns:

true, if this signature algorithm does not know about the verification key.

removeSignumAndAlign20

protected byte[] removeSignumAndAlign20(byte[] signedInteger)

Receives the byte representation of a POSITIVE integer value as two's-complement representation. If the sign bit occupies a whole byte of its own (the least significant byte of the array), this byte is removed. Finally bytes with value 0 are added until the length of the byte array reaches a value of 20. For instance, the hex value "001B" is firstly changed to "1B", finally it will be expanded to "000000000000000000000000000000000000001B".

Please note:

• Parameter signedInteger must not contain more than 21 bytes.
• Parameter signedInteger must not represent a negative integer.

Parameters:

signedInteger - The two's-complement byte representation of a POSITIVE integer value.

Returns:

the expanded representation as shown above.