Added in API level 1

Signature

abstract class Signature : SignatureSpi

kotlin.Any
↳	java.security.SignatureSpi
	↳	java.security.Signature

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-1. The DSA algorithm using the SHA-1 message digest algorithm can be specified as SHA1withDSA. In the case of RSA, there are multiple choices for the message digest algorithm, so the signing algorithm could be specified as, for example, MD2withRSA, MD5withRSA, or SHA1withRSA. 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) and initSign(PrivateKey,SecureRandom)).
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 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.

Android provides the following Signature algorithms:

Algorithm	Supported API Levels
DSA	1+
DSAwithSHA1	1+
DSS	1-19
ECDSA	11+
ECDSAwithSHA1	11+
Ed25519	33+
MD2withRSA	1-3
MD4withRSA	1-8
MD5withRSA	1+
MD5withRSA/ISO9796-2	1-8
NONEwithDSA	1+
NONEwithECDSA	11+
NONEwithRSA	17+
RSASSA-PSS	1-8
SHA1withDSA	1+
SHA1withECDSA	11+
SHA1withRSA	1+
SHA1withRSA/ISO9796-2	1-8
SHA1withRSA/PSS	23+
SHA224withDSA	20+
SHA224withECDSA	20+
SHA224withRSA	20+
SHA224withRSA/PSS	23+
SHA256withDSA	1+
SHA256withECDSA	11+
SHA256withRSA	1+
SHA256withRSA/PSS	23+
SHA384withECDSA	11+
SHA384withRSA	1+
SHA384withRSA/PSS	23+
SHA512withECDSA	11+
SHA512withRSA	1+
SHA512withRSA/PSS	23+

These algorithms are described in the Signature section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

Summary

Constants
static Int	`SIGN` Possible `state` value, signifying that this signature object has been initialized for signing.
static Int	`UNINITIALIZED` Possible `state` value, signifying that this signature object has not yet been initialized.
static Int	`VERIFY` Possible `state` value, signifying that this signature object has been initialized for verification.

Protected constructors
`Signature(algorithm: String!)` Creates a Signature object for the specified algorithm.

Public methods
open Any!	`clone()` Returns a clone if the implementation is cloneable.
String!	`getAlgorithm()` Returns the name of the algorithm for this signature object.
open static Signature!	`getInstance(algorithm: String!)` Returns a Signature object that implements the specified signature algorithm.
open static Signature!	`getInstance(algorithm: String!, provider: String!)` Returns a Signature object that implements the specified signature algorithm.
open static Signature!	`getInstance(algorithm: String!, provider: Provider!)` Returns a Signature object that implements the specified signature algorithm.
Any!	`getParameter(param: String!)` Gets the value of the specified algorithm parameter.
AlgorithmParameters!	`getParameters()` Returns the parameters used with this signature object.
Provider!	`getProvider()` Returns the provider of this signature object.
Unit	`initSign(privateKey: PrivateKey!)` Initialize this object for signing.
Unit	`initSign(privateKey: PrivateKey!, random: SecureRandom!)` Initialize this object for signing.
Unit	`initVerify(certificate: Certificate!)` Initializes this object for verification, using the public key from the given certificate.
Unit	`initVerify(publicKey: PublicKey!)` Initializes this object for verification.
Unit	`setParameter(param: String!, value: Any!)` Sets the specified algorithm parameter to the specified value.
Unit	`setParameter(params: AlgorithmParameterSpec!)` Initializes this signature engine with the specified parameter set.
ByteArray!	`sign()` Returns the signature bytes of all the data updated.
Int	`sign(outbuf: ByteArray!, offset: Int, len: Int)` Finishes the signature operation and stores the resulting signature bytes in the provided buffer `outbuf`, starting at `offset`.
open 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.
Unit	`update(b: Byte)` Updates the data to be signed or verified by a byte.
Unit	`update(data: ByteArray!)` Updates the data to be signed or verified, using the specified array of bytes.
Unit	`update(data: ByteArray!, off: Int, len: Int)` Updates the data to be signed or verified, using the specified array of bytes, starting at the specified offset.
Unit	`update(data: ByteBuffer!)` Updates the data to be signed or verified using the specified ByteBuffer.
Boolean	`verify(signature: ByteArray!)` Verifies the passed-in signature.
Boolean	`verify(signature: ByteArray!, offset: Int, length: Int)` Verifies the passed-in signature in the specified array of bytes, starting at the specified offset.

Inherited functions

From class SignatureSpi

`Any!`	`engineGetParameter(param: String!)` 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.
`AlgorithmParameters!`	`engineGetParameters()` This method is overridden by providers to return the parameters used with this signature engine, or null if this signature engine does not use any parameters. The returned parameters may be the same that were used to initialize this signature engine, or may contain a combination of default and randomly generated parameter values used by the underlying signature implementation if this signature engine requires algorithm parameters but was not initialized with any.
`Unit`	`engineInitSign(privateKey: PrivateKey!)` Initializes this signature object with the specified private key for signing operations.
`Unit`	`engineInitSign(privateKey: PrivateKey!, random: SecureRandom!)` Initializes this signature object with the specified private key and source of randomness for signing operations. This concrete method has been added to this previously-defined abstract class. (For backwards compatibility, it cannot be abstract.)
`Unit`	`engineInitVerify(publicKey: PublicKey!)` Initializes this signature object with the specified public key for verification operations.
`Unit`	`engineSetParameter(param: String!, value: Any!)` 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.
`Unit`	`engineSetParameter(params: AlgorithmParameterSpec!)` This method is overridden by providers to initialize this signature engine with the specified parameter set.
`ByteArray!`	`engineSign()` Returns the signature bytes of all the data updated so far. The format of the signature depends on the underlying signature scheme.
`Int`	`engineSign(outbuf: ByteArray!, offset: Int, len: Int)` Finishes this 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. The signature implementation is reset to its initial state (the state it was in after a call to one of the `engineInitSign` methods) and can be reused to generate further signatures with the same private key. This method should be abstract, but we leave it concrete for binary compatibility. Knowledgeable providers should override this method.
`Unit`	`engineUpdate(b: Byte)` Updates the data to be signed or verified using the specified byte.
`Unit`	`engineUpdate(b: ByteArray!, off: Int, len: Int)` Updates the data to be signed or verified, using the specified array of bytes, starting at the specified offset.
`Unit`	`engineUpdate(input: ByteBuffer!)` Updates the data to be signed or verified using the specified ByteBuffer. Processes the `data.remaining()` bytes starting at at `data.position()`. Upon return, the buffer's position will be equal to its limit; its limit will not have changed.
`Boolean`	`engineVerify(sigBytes: ByteArray!)` Verifies the passed-in signature.
`Boolean`	`engineVerify(sigBytes: ByteArray!, offset: Int, length: Int)` Verifies the passed-in signature in the specified array of bytes, starting at the specified offset. Note: Subclasses should overwrite the default implementation.

Properties
Int	`state` Current state of this signature object.

Inherited properties

From class SignatureSpi

SecureRandom!

appRandom

Application-specified source of randomness.

Constants

SIGN

Added in API level 1

protected static val SIGN: Int

Possible state value, signifying that this signature object has been initialized for signing.

Value: 2

UNINITIALIZED

Added in API level 1

protected static val UNINITIALIZED: Int

Possible state value, signifying that this signature object has not yet been initialized.

Value: 0

VERIFY

Added in API level 1

protected static val VERIFY: Int

Possible state value, signifying that this signature object has been initialized for verification.

Value: 3

Protected constructors

Signature

Added in API level 1

protected Signature(algorithm: String!)

Creates a Signature object for the specified algorithm.

Parameters
`algorithm`	String!: the standard string name of the algorithm. See the Signature section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

Public methods

clone

Added in API level 1

open fun clone(): Any!

Returns a clone if the implementation is cloneable.

Return
`Any!`	a clone if the implementation is cloneable.

Exceptions
`java.lang.CloneNotSupportedException`	if this is called on an implementation that does not support `Cloneable`.

getAlgorithm

Added in API level 1

fun getAlgorithm(): String!

Returns the name of the algorithm for this signature object.

Return
`String!`	the name of the algorithm for this signature object.

getInstance

Added in API level 1

open static fun getInstance(algorithm: String!): Signature!

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.

Parameters
`algorithm`	String!: the standard name of the algorithm requested. See the Signature section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

Return
`Signature!`	the new Signature object.

Exceptions
`java.security.NoSuchAlgorithmException`	if no Provider supports a Signature implementation for the specified algorithm.

See Also

java.security.Provider

getInstance

Added in API level 1

open static fun getInstance(
    algorithm: String!, 
    provider: String!
): Signature!

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`	String!: the name of the algorithm requested. See the Signature section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
`provider`	String!: the name of the provider.

Return
`Signature!`	the new Signature object.

Exceptions
`java.lang.IllegalArgumentException`	if the provider name is null or empty.
`java.security.NoSuchAlgorithmException`	if a SignatureSpi implementation for the specified algorithm is not available from the specified provider.
`java.security.NoSuchProviderException`	if the specified provider is not registered in the security provider list.

See Also

java.security.Provider

getInstance

Added in API level 1

open static fun getInstance(
    algorithm: String!, 
    provider: Provider!
): Signature!

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`	String!: the name of the algorithm requested. See the Signature section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
`provider`	Provider!: the provider.

Return
`Signature!`	the new Signature object.

Exceptions
`java.lang.IllegalArgumentException`	if the provider is null.
`java.security.NoSuchAlgorithmException`	if a SignatureSpi implementation for the specified algorithm is not available from the specified Provider object.

See Also

java.security.Provider

getParameter

Added in API level 1
Deprecated in API level 15

fun getParameter(param: String!): Any!

Deprecated: Deprecated.

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`	String!: the string name of the parameter.

Return
`Any!`	the object that represents the parameter value, or null if there is none.

Exceptions
`java.security.InvalidParameterException`	if `param` is an invalid parameter for this engine, or another exception occurs while trying to get this parameter.

See Also

#setParameter(java.lang.String,java.lang.Object)

getParameters

Added in API level 1

fun getParameters(): AlgorithmParameters!

Returns the parameters used with this signature object.

The returned parameters may be the same that were used to initialize this signature, or may contain a combination of default and randomly generated parameter values used by the underlying signature implementation if this signature requires algorithm parameters but was not initialized with any.

Return
`AlgorithmParameters!`	the parameters used with this signature, or null if this signature does not use any parameters.

See Also

#setParameter(java.security.spec.AlgorithmParameterSpec)

getProvider

Added in API level 1

fun getProvider(): Provider!

Returns the provider of this signature object.

Return
`Provider!`	the provider of this signature object

initSign

Added in API level 1

fun initSign(privateKey: PrivateKey!): Unit

Initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.

Parameters
`privateKey`	PrivateKey!: the private key of the identity whose signature is going to be generated.

Exceptions
`java.security.InvalidKeyException`	if the key is invalid.

initSign

Added in API level 1

fun initSign(
    privateKey: PrivateKey!, 
    random: SecureRandom!
): Unit

Initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.

Parameters
`privateKey`	PrivateKey!: the private key of the identity whose signature is going to be generated.
`random`	SecureRandom!: the source of randomness for this signature.

Exceptions
`java.security.InvalidKeyException`	if the key is invalid.

initVerify

Added in API level 1

fun initVerify(certificate: Certificate!): Unit

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`	Certificate!: the certificate of the identity whose signature is going to be verified.

Exceptions
`java.security.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.

initVerify

Added in API level 1

fun initVerify(publicKey: PublicKey!): Unit

Initializes this object for verification. If this method is called again with a different argument, it negates the effect of this call.

Parameters
`publicKey`	PublicKey!: the public key of the identity whose signature is going to be verified.

Exceptions
`java.security.InvalidKeyException`	if the key is invalid.

setParameter

Added in API level 1
Deprecated in API level 15

fun setParameter(
    param: String!, 
    value: Any!
): Unit

Deprecated: Use 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`	String!: the string identifier of the parameter.
`value</`