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:

  1. Initialization, with either
  2. Updating

    Depending on the type of initialization, this will update the bytes to be signed or verified. See the update methods.

  3. 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

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

static Int

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

static Int

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!

Returns a clone if the implementation is cloneable.

String!

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!

Gets the value of the specified algorithm parameter.

AlgorithmParameters!

Returns the parameters used with this signature object.

Provider!

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(publicKey: PublicKey!)

Initializes this object for verification.

Unit
initVerify(certificate: Certificate!)

Initializes this object for verification, using the public key from the given certificate.

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

Sets the specified algorithm parameter to the specified value.

Unit

Initializes this signature engine with the specified parameter set.

ByteArray!

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

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

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

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
Properties
Int

Current state of this signature object.

Inherited properties

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 the object's class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned.
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.

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.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.
java.lang.IllegalArgumentException if the provider name is null or empty.

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

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.

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.

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(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.

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.

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 Any!: the parameter value.
Exceptions
java.security.InvalidParameterException if param 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

setParameter

Added in API level 1
fun setParameter(params: AlgorithmParameterSpec!): Unit

Initializes this signature engine with the specified parameter set.

Parameters
params AlgorithmParameterSpec!: the parameters
Exceptions
java.security.InvalidAlgorithmParameterException if the given parameters are inappropriate for this signature engine

See Also

sign

Added in API level 1
fun sign(): ByteArray!

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.

Return
ByteArray! the signature bytes of the signing operation's result.
Exceptions
java.security.SignatureException if this signature object is not initialized properly or if this signature algorithm is unable to process the input data provided.

sign

Added in API level 1
fun sign(
    outbuf: ByteArray!,
    offset: Int,
    len: Int
): Int

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 ByteArray!: buffer for the signature result.
offset Int: offset into outbuf where the signature is stored.
len Int: number of bytes within outbuf allotted for the signature.
Return
Int the number of bytes placed into outbuf.
Exceptions
java.security.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.

toString

Added in API level 1
open fun toString(): String

Returns a string representation of this signature object, providing information that includes the state of the object and the name of the algorithm used.

Return
String a string representation of this signature object.

update

Added in API level 1
fun update(b: Byte): Unit

Updates the data to be signed or verified by a byte.

Parameters
b Byte: the byte to use for the update.
Exceptions
java.security.SignatureException if this signature object is not initialized properly.

update

Added in API level 1
fun update(data: ByteArray!): Unit

Updates the data to be signed or verified, using the specified array of bytes.

Parameters
data ByteArray!: the byte array to use for the update.
Exceptions
java.security.SignatureException if this signature object is not initialized properly.

update

Added in API level 1
fun update(
    data: ByteArray!,
    off: Int,
    len: Int
): Unit

Updates the data to be signed or verified, using the specified array of bytes, starting at the specified offset.

Parameters
data ByteArray!: the array of bytes.
off Int: the offset to start from in the array of bytes.
len Int: the number of bytes to use, starting at offset.
Exceptions
java.security.SignatureException if this signature object is not initialized properly.

update

Added in API level 1
fun update(data: ByteBuffer!): Unit

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.

Parameters
data ByteBuffer!: the ByteBuffer
Exceptions
java.security.SignatureException if this signature object is not initialized properly.

verify

Added in API level 1
fun verify(signature: ByteArray!): Boolean

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 ByteArray!: the signature bytes to be verified.
Return
Boolean true if the signature was verified, false if not.
Exceptions
java.security.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

Added in API level 1
fun verify(
    signature: ByteArray!,
    offset: Int,
    length: Int
): Boolean

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 ByteArray!: the signature bytes to be verified.
offset Int: the offset to start from in the array of bytes.
length Int: the number of bytes to use, starting at offset.
Return
Boolean true if the signature was verified, false if not.
Exceptions
java.security.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.
java.lang.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.

Properties

state

Added in API level 1
protected var state: Int

Current state of this signature object.