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(java.security.PrivateKey)
andinitSign(java.security.PrivateKey,java.security.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.
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+ |
Summary
Constants | |
---|---|
static Int |
Possible |
static Int |
Possible |
static Int |
Possible |
Protected constructors | |
---|---|
Creates a Signature object for the specified algorithm. |
Public methods | |
---|---|
open Any! |
clone() 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! |
getParameter(param: String!) 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(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 |
Finishes the signature operation and stores the resulting signature bytes in the provided buffer |
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 |
Updates the data to be signed or verified by a byte. |
Unit |
Updates the data to be signed or verified, using the specified array of bytes. |
Unit |
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 |
Verifies the passed-in signature. |
Boolean |
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
protected static val SIGN: Int
Possible state
value, signifying that this signature object has been initialized for signing.
Value: 2
UNINITIALIZED
protected static val UNINITIALIZED: Int
Possible state
value, signifying that this signature object has not yet been initialized.
Value: 0
VERIFY
protected static val VERIFY: Int
Possible state
value, signifying that this signature object has been initialized for verification.
Value: 3
Protected constructors
Signature
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
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
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
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
getInstance
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. |
See Also
getInstance
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. |
See Also
getParameter
fungetParameter(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
getParameters
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
fun getProvider(): Provider!
Returns the provider of this signature object.
Return | |
---|---|
Provider! |
the provider of this signature object |
initSign
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
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
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
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
funsetParameter(
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
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
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
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
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
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
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
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
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
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
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. |