public abstract class Signature extends SignatureSpi
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:
initVerify
), or initSign(PrivateKey)
and initSign(PrivateKey, SecureRandom)
). Depending on the type of initialization, this will update the bytes to be signed or verified. See the update
methods.
sign
methods and the verify
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
Modifier and Type | Field | Description |
---|---|---|
protected static final int |
SIGN |
Possible state value, signifying that this Signature object has been initialized for signing. |
protected int |
state |
Current state of this Signature object. |
protected static final int |
UNINITIALIZED |
Possible state value, signifying that this Signature object has not yet been initialized. |
protected static final int |
VERIFY |
Possible state value, signifying that this Signature object has been initialized for verification. |
appRandom
Modifier | Constructor | Description |
---|---|---|
protected |
Creates a Signature object for the specified algorithm. |
Modifier and Type | Method | Description |
---|---|---|
Object |
clone() |
Returns a clone if the implementation is cloneable. |
final String |
getAlgorithm() |
Returns the name of the algorithm for this Signature object. |
static Signature |
getInstance |
Returns a Signature object that implements the specified signature algorithm. |
static Signature |
getInstance |
Returns a Signature object that implements the specified signature algorithm. |
static Signature |
getInstance |
Returns a Signature object that implements the specified signature algorithm. |
final Object |
getParameter |
Deprecated. |
final AlgorithmParameters |
getParameters() |
Returns the parameters used with this Signature object. |
final Provider |
getProvider() |
Returns the provider of this Signature object. |
final void |
initSign |
Initialize this object for signing. |
final void |
initSign |
Initialize this object for signing. |
final void |
initVerify |
Initializes this object for verification, using the public key from the given certificate. |
final void |
initVerify |
Initializes this object for verification. |
final void |
setParameter |
Deprecated. |
final void |
setParameter |
Initializes this Signature object with the specified parameter values. |
final byte[] |
sign() |
Returns the signature bytes of all the data updated. |
final int |
sign |
Finishes the signature operation and stores the resulting signature bytes in the provided buffer outbuf , starting at offset . |
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. |
final void |
update |
Updates the data to be signed or verified by a byte. |
final void |
update |
Updates the data to be signed or verified, using the specified array of bytes. |
final void |
update |
Updates the data to be signed or verified, using the specified array of bytes, starting at the specified offset. |
final void |
update |
Updates the data to be signed or verified using the specified ByteBuffer. |
final boolean |
verify |
Verifies the passed-in signature. |
final boolean |
verify |
Verifies the passed-in signature in the specified array of bytes, starting at the specified offset. |
engineGetParameter, engineGetParameters, engineInitSign, engineInitSign, engineInitVerify, engineSetParameter, engineSetParameter, engineSign, engineSign, engineUpdate, engineUpdate, engineUpdate, engineVerify, engineVerify
protected static final int UNINITIALIZED
state
value, signifying that this Signature
object has not yet been initialized.protected static final int SIGN
state
value, signifying that this Signature
object has been initialized for signing.protected static final int VERIFY
state
value, signifying that this Signature
object has been initialized for verification.protected int state
Signature
object.protected Signature(String algorithm)
Signature
object for the specified algorithm.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.public static Signature getInstance(String algorithm) throws NoSuchAlgorithmException
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.
jdk.security.provider.preferred
Security
property to determine the preferred provider order for the specified algorithm. This may be different from the order of providers returned by Security.getProviders()
.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.Signature
objectNoSuchAlgorithmException
- if no Provider
supports a Signature
implementation for the specified algorithmNullPointerException
- if algorithm
is null
public static Signature getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
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.
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.Signature
objectIllegalArgumentException
- if the provider name is null
or emptyNoSuchAlgorithmException
- if a SignatureSpi
implementation for the specified algorithm is not available from the specified providerNoSuchProviderException
- if the specified provider is not registered in the security provider listNullPointerException
- if algorithm
is null
public static Signature getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
Signature
object that implements the specified signature algorithm. A new Signature
object encapsulating the SignatureSpi
implementation from the specified provider is returned. Note that the specified provider does not have to be registered in the provider list.
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.Signature
objectIllegalArgumentException
- if the provider is null
NoSuchAlgorithmException
- if a SignatureSpi
implementation for the specified algorithm is not available from the specified Provider
objectNullPointerException
- if algorithm
is null
public final Provider getProvider()
Signature
object.Signature
objectpublic final void initVerify(PublicKey publicKey) throws InvalidKeyException
publicKey
- the public key of the identity whose signature is going to be verified.InvalidKeyException
- if the key is invalid.public final void initVerify(Certificate certificate) throws InvalidKeyException
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.
certificate
- the certificate of the identity whose signature is going to be verified.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.public final void initSign(PrivateKey privateKey) throws InvalidKeyException
privateKey
- the private key of the identity whose signature is going to be generated.InvalidKeyException
- if the key is invalid.public final void initSign(PrivateKey privateKey, SecureRandom random) throws InvalidKeyException
privateKey
- the private key of the identity whose signature is going to be generatedrandom
- the source of randomness for this Signature
objectInvalidKeyException
- if the key is invalid.public final byte[] sign() throws SignatureException
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
.
SignatureException
- if this Signature
object is not initialized properly or if this signature algorithm is unable to process the input data provided.public final int sign(byte[] outbuf, int offset, int len) throws SignatureException
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.
outbuf
- buffer for the signature result.offset
- offset into outbuf
where the signature is stored.len
- number of bytes within outbuf
allotted for the signature.outbuf
.SignatureException
- if this Signature
object is not initialized properly, if this signature algorithm is unable to process the input data provided, or if len
is less than the actual signature length.IllegalArgumentException
- if outbuf
is null
, or offset
or len
is less than 0, or the sum of offset
and len
is greater than the length of outbuf
.public final boolean verify(byte[] signature) throws SignatureException
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
.
signature
- the signature bytes to be verified.true
if the signature was verified, false
if not.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.public final boolean verify(byte[] signature, int offset, int length) throws SignatureException
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
.
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.true
if the signature was verified, false
if not.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 the signature
byte array is null
, or the offset
or length
is less than 0, or the sum of the offset
and length
is greater than the length of the signature
byte array.public final void update(byte b) throws SignatureException
b
- the byte to use for the update.SignatureException
- if this Signature
object is not initialized properly.public final void update(byte[] data) throws SignatureException
data
- the byte array to use for the update.SignatureException
- if this Signature
object is not initialized properly.public final void update(byte[] data, int off, int len) throws SignatureException
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.SignatureException
- if this Signature
object is not initialized properly.IllegalArgumentException
- if data
is null
, or off
or len
is less than 0, or the sum of off
and len
is greater than the length of data
.public final void update(ByteBuffer data) throws SignatureException
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.data
- the ByteBufferSignatureException
- if this Signature
object is not initialized properly.public final String getAlgorithm()
Signature
object.Signature
object.public String toString()
Signature
object, providing information that includes the state of the object and the name of the algorithm used.@Deprecated public final void setParameter(String param, Object value) throws InvalidParameterException
setParameter
.param
- the string identifier of the parametervalue
- the parameter valueInvalidParameterException
- if param
is an invalid parameter for this Signature
object, the parameter is already set and cannot be set again, a security exception occurs, and so on.public final void setParameter(AlgorithmParameterSpec params) throws InvalidAlgorithmParameterException
Signature
object with the specified parameter values.params
- the parameter valuesInvalidAlgorithmParameterException
- if the given parameter values are inappropriate for this Signature
objectpublic final AlgorithmParameters getParameters()
Signature
object. The returned parameters may be the same that were used to initialize this Signature
object, or may contain additional default or random parameter values used by the underlying signature scheme. If the required parameters were not supplied and can be generated by the Signature
object, the generated parameters are returned; otherwise null
is returned.
However, if the signature scheme does not support returning the parameters as AlgorithmParameters
, null
is always returned.
Signature
object, or null
UnsupportedOperationException
- if the provider does not support this method@Deprecated public final Object getParameter(String param) throws InvalidParameterException
param
- the string name of the parameter.null
if there is none.InvalidParameterException
- if param
is an invalid parameter for this engine, or another exception occurs while trying to get this parameter.public Object clone() throws CloneNotSupportedException
clone
in class SignatureSpi
CloneNotSupportedException
- if this is called on an implementation that does not support Cloneable
.
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/security/Signature.html
setParameter
.