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-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:

Name Supported (API Levels)
DSA 1+
DSAwithSHA1 1+
DSS 1–19
ECDSA 11+
ECDSAwithSHA1 11+
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
SHA256withECDSA 11+
SHA256withRSA 1+
SHA384withECDSA 11+
SHA384withRSA 1+
SHA512withECDSA 11+
SHA512withRSA 1+
These algorithms are described in the Signature section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

Constant Summary

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

Field Summary

protected int state Current state of this signature object.

Inherited Field Summary

Protected Constructor Summary

Signature(String algorithm)
Creates a Signature object for the specified algorithm.

Public Method Summary

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(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.
final Object
getParameter(String param)
This method was deprecated. 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(PrivateKey privateKey, SecureRandom random)
Initialize this object for signing.
final void
initSign(PrivateKey privateKey)
Initialize this object for signing.
final void
initVerify(PublicKey publicKey)
Initializes this object for verification.
final void
initVerify(Certificate certificate)
Initializes this object for verification, using the public key from the given certificate.
final void
setParameter(AlgorithmParameterSpec params)
Initializes this signature engine with the specified parameter set.
final void
setParameter(String param, Object value)
This method was deprecated. Use setParameter.
final int
sign(byte[] outbuf, int offset, int len)
Finishes the signature operation and stores the resulting signature bytes in the provided buffer outbuf, starting at offset.
final byte[]
sign()
Returns the signature bytes of all the data updated.
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(byte[] data)
Updates the data to be signed or verified, using the specified array of bytes.
final 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.
final void
update(ByteBuffer data)
Updates the data to be signed or verified using the specified ByteBuffer.
final void
update(byte b)
Updates the data to be signed or verified by a byte.
final boolean
verify(byte[] signature, int offset, int length)
Verifies the passed-in signature in the specified array of bytes, starting at the specified offset.
final boolean
verify(byte[] signature)
Verifies the passed-in signature.

Inherited Method Summary