Class Signature
- java.lang.Object
-
- java.security.SignatureSpi
-
- java.security.Signature
public abstract class Signature extends SignatureSpi
The Signature class is used to provide applications the functionality of a digital signature algorithm. Digital signatures are used for authentication and integrity assurance of digital data.
The signature algorithm can be, among others, the NIST standard DSA, using DSA and SHA-256. The DSA algorithm using the SHA-256 message digest algorithm can be specified as SHA256withDSA
. In the case of RSA the signing algorithm could be specified as, for example, SHA256withRSA
. The algorithm name must be specified, as there is no default.
A Signature object can be used to generate and verify digital signatures.
There are three phases to the use of a Signature object for either signing data or verifying a signature:
- Initialization, with either
- a public key, which initializes the signature for verification (see
initVerify
), or - a private key (and optionally a Secure Random Number Generator), which initializes the signature for signing (see
initSign(PrivateKey)
andinitSign(PrivateKey, SecureRandom)
).
- a public key, which initializes the signature for verification (see
- Updating
Depending on the type of initialization, this will update the bytes to be signed or verified. See the
update
methods. - Signing or Verifying a signature on all updated bytes. See the
sign
methods and theverify
method.
Note that this class is abstract and extends from SignatureSpi
for historical reasons. Application developers should only take notice of the methods defined in this Signature
class; all the methods in the superclass are intended for cryptographic service providers who wish to supply their own implementations of digital signature algorithms.
Every implementation of the Java platform is required to support the following standard Signature
algorithms:
SHA1withDSA
SHA256withDSA
SHA1withRSA
SHA256withRSA
- Since:
- 1.1
Field Summary
Modifier and Type | Field | Description |
---|---|---|
protected static int | SIGN | Possible |
protected int | state | Current state of this signature object. |
protected static int | UNINITIALIZED | Possible |
protected static int | VERIFY | Possible |
Fields declared in class java.security.SignatureSpi
appRandom
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | Signature(String algorithm) | Creates a Signature object for the specified algorithm. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
Object | clone() | Returns a clone if the implementation is cloneable. |
String | getAlgorithm() | Returns the name of the algorithm for this signature object. |
static Signature | getInstance(String algorithm) | Returns a Signature object that implements the specified signature algorithm. |
static Signature | getInstance(String algorithm,
String provider) | Returns a Signature object that implements the specified signature algorithm. |
static Signature | getInstance(String algorithm,
Provider provider) | Returns a Signature object that implements the specified signature algorithm. |
Object | getParameter(String param) | Deprecated. |
AlgorithmParameters | getParameters() | Returns the parameters used with this signature object. |
Provider | getProvider() | Returns the provider of this signature object. |
void | initSign(PrivateKey privateKey) | Initialize this object for signing. |
void | initSign(PrivateKey privateKey,
SecureRandom random) | Initialize this object for signing. |
void | initVerify(Certificate certificate) | Initializes this object for verification, using the public key from the given certificate. |
void | initVerify(PublicKey publicKey) | Initializes this object for verification. |
void | setParameter(String param,
Object value) | Deprecated. Use setParameter . |
void | setParameter(AlgorithmParameterSpec params) | Initializes this signature engine with the specified parameter set. |
byte[] | sign() | Returns the signature bytes of all the data updated. |
int | sign(byte[] outbuf,
int offset,
int len) | Finishes the signature operation and stores the resulting signature bytes in the provided buffer |
String | toString() | Returns a string representation of this signature object, providing information that includes the state of the object and the name of the algorithm used. |
void | update(byte b) | Updates the data to be signed or verified by a byte. |
void | update(byte[] data) | Updates the data to be signed or verified, using the specified array of bytes. |
void | update(byte[] data,
int off,
int len) | Updates the data to be signed or verified, using the specified array of bytes, starting at the specified offset. |
void | update(ByteBuffer data) | Updates the data to be signed or verified using the specified ByteBuffer. |
boolean | verify(byte[] signature) | Verifies the passed-in signature. |
boolean | verify(byte[] signature,
int offset,
int length) | Verifies the passed-in signature in the specified array of bytes, starting at the specified offset. |
Methods declared in class java.security.SignatureSpi
engineGetParameter, engineGetParameters, engineInitSign, engineInitSign, engineInitVerify, engineSetParameter, engineSetParameter, engineSign, engineSign, engineUpdate, engineUpdate, engineUpdate, engineVerify, engineVerify
Methods declared in class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Field Detail
UNINITIALIZED
protected static final int UNINITIALIZED
Possible state
value, signifying that this signature object has not yet been initialized.
- See Also:
- Constant Field Values
SIGN
protected static final int SIGN
Possible state
value, signifying that this signature object has been initialized for signing.
- See Also:
- Constant Field Values
VERIFY
protected static final int VERIFY
Possible state
value, signifying that this signature object has been initialized for verification.
- See Also:
- Constant Field Values
state
protected int state
Current state of this signature object.
Constructor Detail
Signature
protected Signature(String algorithm)
Creates a Signature object for the specified algorithm.
- Parameters:
-
algorithm
- the standard string name of the algorithm. See the Signature section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
Method Detail
getInstance
public static Signature getInstance(String algorithm) throws NoSuchAlgorithmException
Returns a Signature object that implements the specified signature algorithm.
This method traverses the list of registered security Providers, starting with the most preferred Provider. A new Signature object encapsulating the SignatureSpi implementation from the first Provider that supports the specified algorithm is returned.
Note that the list of registered providers may be retrieved via the Security.getProviders()
method.
- Implementation Note:
- The JDK Reference Implementation additionally uses the
jdk.security.provider.preferred
Security
property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned bySecurity.getProviders()
. - Parameters:
-
algorithm
- the standard name of the algorithm requested. See the Signature section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names. - Returns:
- the new
Signature
object - Throws:
-
NoSuchAlgorithmException
- if noProvider
supports aSignature
implementation for the specified algorithm -
NullPointerException
- ifalgorithm
isnull
- See Also:
Provider
getInstance
public static Signature getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
Returns a Signature object that implements the specified signature algorithm.
A new Signature object encapsulating the SignatureSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.
Note that the list of registered providers may be retrieved via the Security.getProviders()
method.
- Parameters:
-
algorithm
- the name of the algorithm requested. See the Signature section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names. -
provider
- the name of the provider. - Returns:
- the new
Signature
object - Throws:
-
IllegalArgumentException
- if the provider name isnull
or empty -
NoSuchAlgorithmException
- if aSignatureSpi
implementation for the specified algorithm is not available from the specified provider -
NoSuchProviderException
- if the specified provider is not registered in the security provider list -
NullPointerException
- ifalgorithm
isnull
- See Also:
Provider
getInstance
public static Signature getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
Returns a Signature object that implements the specified signature algorithm.
A new Signature object encapsulating the SignatureSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.
- Parameters:
-
algorithm
- the name of the algorithm requested. See the Signature section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names. -
provider
- the provider. - Returns:
- the new
Signature
object - Throws:
-
IllegalArgumentException
- if the provider isnull
-
NoSuchAlgorithmException
- if aSignatureSpi
implementation for the specified algorithm is not available from the specifiedProvider
object -
NullPointerException
- ifalgorithm
isnull
- Since:
- 1.4
- See Also:
Provider
getProvider
public final Provider getProvider()
Returns the provider of this signature object.
- Returns:
- the provider of this signature object
initVerify
public final void initVerify(PublicKey publicKey) throws InvalidKeyException
Initializes this object for verification. If this method is called again with a different argument, it negates the effect of this call.
- Parameters:
-
publicKey
- the public key of the identity whose signature is going to be verified. - Throws:
-
InvalidKeyException
- if the key is invalid.
initVerify
public final void initVerify(Certificate certificate) throws InvalidKeyException
Initializes this object for verification, using the public key from the given certificate.
If the certificate is of type X.509 and has a key usage extension field marked as critical, and the value of the key usage extension field implies that the public key in the certificate and its corresponding private key are not supposed to be used for digital signatures, an InvalidKeyException
is thrown.
- Parameters:
-
certificate
- the certificate of the identity whose signature is going to be verified. - Throws:
-
InvalidKeyException
- if the public key in the certificate is not encoded properly or does not include required parameter information or cannot be used for digital signature purposes. - Since:
- 1.3
initSign
public final void initSign(PrivateKey privateKey) throws InvalidKeyException
Initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.
- Parameters:
-
privateKey
- the private key of the identity whose signature is going to be generated. - Throws:
-
InvalidKeyException
- if the key is invalid.
initSign
public final void initSign(PrivateKey privateKey, SecureRandom random) throws InvalidKeyException
Initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.
- Parameters:
-
privateKey
- the private key of the identity whose signature is going to be generated. -
random
- the source of randomness for this signature. - Throws:
-
InvalidKeyException
- if the key is invalid.
sign
public final byte[] sign() throws SignatureException
Returns the signature bytes of all the data updated. The format of the signature depends on the underlying signature scheme.
A call to this method resets this signature object to the state it was in when previously initialized for signing via a call to initSign(PrivateKey)
. That is, the object is reset and available to generate another signature from the same signer, if desired, via new calls to update
and sign
.
- Returns:
- the signature bytes of the signing operation's result.
- Throws:
-
SignatureException
- if this signature object is not initialized properly or if this signature algorithm is unable to process the input data provided.
sign
public final int sign(byte[] outbuf, int offset, int len) throws SignatureException
Finishes the signature operation and stores the resulting signature bytes in the provided buffer outbuf
, starting at offset
. The format of the signature depends on the underlying signature scheme.
This signature object is reset to its initial state (the state it was in after a call to one of the initSign
methods) and can be reused to generate further signatures with the same private key.
- Parameters:
-
outbuf
- buffer for the signature result. -
offset
- offset intooutbuf
where the signature is stored. -
len
- number of bytes withinoutbuf
allotted for the signature. - Returns:
- the number of bytes placed into
outbuf
. - Throws:
-
SignatureException
- if this signature object is not initialized properly, if this signature algorithm is unable to process the input data provided, or iflen
is less than the actual signature length. -
IllegalArgumentException
- ifoutbuf
isnull
, oroffset
orlen
is less than 0, or the sum ofoffset
andlen
is greater than the length ofoutbuf
. - Since:
- 1.2
verify
public final boolean verify(byte[] signature) throws SignatureException
Verifies the passed-in signature.
A call to this method resets this signature object to the state it was in when previously initialized for verification via a call to initVerify(PublicKey)
. That is, the object is reset and available to verify another signature from the identity whose public key was specified in the call to initVerify
.
- Parameters:
-
signature
- the signature bytes to be verified. - Returns:
- true if the signature was verified, false if not.
- Throws:
-
SignatureException
- if this signature object is not initialized properly, the passed-in signature is improperly encoded or of the wrong type, if this signature algorithm is unable to process the input data provided, etc.
verify
public final boolean verify(byte[] signature, int offset, int length) throws SignatureException
Verifies the passed-in signature in the specified array of bytes, starting at the specified offset.
A call to this method resets this signature object to the state it was in when previously initialized for verification via a call to initVerify(PublicKey)
. That is, the object is reset and available to verify another signature from the identity whose public key was specified in the call to initVerify
.
- Parameters:
-
signature
- the signature bytes to be verified. -
offset
- the offset to start from in the array of bytes. -
length
- the number of bytes to use, starting at offset. - Returns:
- true if the signature was verified, false if not.
- Throws:
-
SignatureException
- if this signature object is not initialized properly, the passed-in signature is improperly encoded or of the wrong type, if this signature algorithm is unable to process the input data provided, etc. -
IllegalArgumentException
- if thesignature
byte array isnull
, or theoffset
orlength
is less than 0, or the sum of theoffset
andlength
is greater than the length of thesignature
byte array. - Since:
- 1.4
update
public final void update(byte b) throws SignatureException
Updates the data to be signed or verified by a byte.
- Parameters:
-
b
- the byte to use for the update. - Throws:
-
SignatureException
- if this signature object is not initialized properly.
update
public final void update(byte[] data) throws SignatureException
Updates the data to be signed or verified, using the specified array of bytes.
- Parameters:
-
data
- the byte array to use for the update. - Throws:
-
SignatureException
- if this signature object is not initialized properly.
update
public final void update(byte[] data, int off, int len) throws SignatureException
Updates the data to be signed or verified, using the specified array of bytes, starting at the specified offset.
- Parameters:
-
data
- the array of bytes. -
off
- the offset to start from in the array of bytes. -
len
- the number of bytes to use, starting at offset. - Throws:
-
SignatureException
- if this signature object is not initialized properly. -
IllegalArgumentException
- ifdata
isnull
, oroff
orlen
is less than 0, or the sum ofoff
andlen
is greater than the length ofdata
.
update
public final void update(ByteBuffer data) throws SignatureException
Updates the data to be signed or verified using the specified ByteBuffer. Processes the data.remaining()
bytes starting at data.position()
. Upon return, the buffer's position will be equal to its limit; its limit will not have changed.
- Parameters:
-
data
- the ByteBuffer - Throws:
-
SignatureException
- if this signature object is not initialized properly. - Since:
- 1.5
getAlgorithm
public final String getAlgorithm()
Returns the name of the algorithm for this signature object.
- Returns:
- the name of the algorithm for this signature object.
toString
public String toString()
Returns a string representation of this signature object, providing information that includes the state of the object and the name of the algorithm used.
setParameter
@Deprecated public final void setParameter(String param, Object value) throws InvalidParameterException
setParameter
.Sets the specified algorithm parameter to the specified value. This method supplies a general-purpose mechanism through which it is possible to set the various parameters of this object. A parameter may be any settable parameter for the algorithm, such as a parameter size, or a source of random bits for signature generation (if appropriate), or an indication of whether or not to perform a specific but optional computation. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.
- Parameters:
-
param
- the string identifier of the parameter. -
value
- the parameter value. - Throws:
-
InvalidParameterException
- ifparam
is an invalid parameter for this signature algorithm engine, the parameter is already set and cannot be set again, a security exception occurs, and so on. - See Also:
getParameter(java.lang.String)
setParameter
public final void setParameter(AlgorithmParameterSpec params) throws InvalidAlgorithmParameterException
Initializes this signature engine with the specified parameter set.
- Parameters:
-
params
- the parameters - Throws:
-
InvalidAlgorithmParameterException
- if the given parameters are inappropriate for this signature engine - See Also:
getParameters()
getParameters
public final AlgorithmParameters getParameters()
Returns the parameters used with this signature object.
If this signature has been previously initialized with parameters (by calling the setParameter
method), this method returns the same parameters. If this signature has not been initialized with parameters, this method may return a combination of default and randomly generated parameter values if the underlying signature implementation supports it and can successfully generate them. Otherwise, null
is returned.
- Returns:
- the parameters used with this signature, or
null
- Since:
- 1.4
- See Also:
setParameter(AlgorithmParameterSpec)
getParameter
@Deprecated public final Object getParameter(String param) throws InvalidParameterException
Gets the value of the specified algorithm parameter. This method supplies a general-purpose mechanism through which it is possible to get the various parameters of this object. A parameter may be any settable parameter for the algorithm, such as a parameter size, or a source of random bits for signature generation (if appropriate), or an indication of whether or not to perform a specific but optional computation. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.
- Parameters:
-
param
- the string name of the parameter. - Returns:
- the object that represents the parameter value, or
null
if there is none. - Throws:
-
InvalidParameterException
- ifparam
is an invalid parameter for this engine, or another exception occurs while trying to get this parameter. - See Also:
setParameter(String, Object)
clone
public Object clone() throws CloneNotSupportedException
Returns a clone if the implementation is cloneable.
- Overrides:
-
clone
in classSignatureSpi
- Returns:
- a clone if the implementation is cloneable.
- Throws:
-
CloneNotSupportedException
- if this is called on an implementation that does not supportCloneable
. - See Also:
Cloneable