Java Signature initSign() method with Examples
initSign(PrivateKey privateKey)
The initSign() method of java.security.Provider class is used to initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.
Syntax:
public final void
initSign(PrivateKey privateKey)
throws InvalidKeyException
Parameters: This method takes the private key of the identity as parameter whose signature is going to be generated
Exception: This method throws InvalidKeyException if the key is invalid.
Below are the examples to illustrate the initSign() method:
Note: The following program will not run in online IDE
Example 1:
// Java program to demonstrate // initSign() method import java.security.*; import java.util.*; import sun.misc.BASE64Encoder; public class GFG1 { public static void main(String[] argv) throws Exception { try { // calling getKeyPair() method and assining in keypair KeyPair keyPair = getKeyPair(); // creating byte array object byte[] outbuff = new byte[1000]; // data to be updated byte[] data = "test".getBytes("UTF8"); // creating the object of Signature Signature sr = Signature.getInstance("SHA1WithRSA"); // initializing the signature object with key pair // for signing // Using method initSign sr.initSign(keyPair.getPrivate()); // updating the data sr.update(data); // getting the signature byte // of an signing operation // by using method sign() byte[] bytes = sr.sign(); // pritning the number of byte System.out.println("Signature:" + Arrays.toString(bytes)); } catch (NoSuchAlgorithmException e) { System.out.println("Exception thrown : " + e); } catch (SignatureException e) { System.out.println("Exception thrown : " + e); } } // defining getKeyPair method private static KeyPair getKeyPair() throws NoSuchAlgorithmException { // creating the object of KeyPairGenerator KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); // initializing with 1024 kpg.initialize(1024); // returning the key pairs return kpg.genKeyPair(); } } |
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Output:
Signature:[-109, -21, 90, -114, -22, .... .... ...., 92, 1]
Example 2: To show InvalidKeyException
// Java program to demonstrate // initSign() method import java.security.*; import java.util.*; public class GFG1 { public static void main(String[] argv) throws Exception { try { // data to be updated byte[] data = "test".getBytes("UTF8"); // creating the object of Signature Signature sr = Signature.getInstance("SHA1WithRSA"); // initializing the signature object with key pair // for signing // Using method initSign System.out.println("Trying to put null as private key "); sr.initSign(null); // updating the data sr.update(data); // getting the signature byte // of an signing operation // by using method sign() byte[] bytes = sr.sign(); // pritning the number of byte System.out.println("Signature:" + Arrays.toString(bytes)); } catch (NoSuchAlgorithmException e) { System.out.println("Exception thrown : " + e); } catch (SignatureException e) { System.out.println("Exception thrown : " + e); } catch (InvalidKeyException e) { System.out.println("Exception thrown : " + e); } } } |
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Output:
Trying to put null as private key Exception thrown : java.security.InvalidKeyException: Key must not be null
initSign(PrivateKey privateKey, SecureRandom random)
The initSign() method of java.security.Provider class is used to initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.
Syntax:
public final void
initSign(PrivateKey privateKey, SecureRandom random)
throws InvalidKeyException
Parameters: This method takes following as a parameters:
- privateKey– the private key of the identity whose signature is going to be generated.
- random– the source of randomness for this signature.
Exception: This method throws InvalidKeyException if the key is invalid.
Below are the examples to illustrate the sign() method:
Note: The following program will not run in online IDE
Example 1:
// Java program to demonstrate // sign() method import java.security.*; import java.util.*; import sun.misc.BASE64Encoder; public class GFG1 { public static void main(String[] argv) throws Exception { try { // calling getKeyPair() method and assining in keypair KeyPair keyPair = getKeyPair(); // creating byte array object byte[] outbuff = new byte[1000]; // data to be updated byte[] data = "test".getBytes("UTF8"); // creating the object of Signature Signature sr = Signature.getInstance("SHA1WithRSA"); // creating the object of SecureRandom SecureRandom sb = SecureRandom.getInstance("SHA1PRNG"); // initializing the signature object with key pair // for signing sr.initSign(keyPair.getPrivate(), sb); // updating the data sr.update(data); // getting the signature byte // of an signing operation // by using method sign() byte[] bytes = sr.sign(); // pritning the number of byte System.out.println("Signature:" + Arrays.toString(bytes)); } catch (NoSuchAlgorithmException e) { System.out.println("Exception thrown : " + e); } catch (SignatureException e) { System.out.println("Exception thrown : " + e); } } // defining getKeyPair method private static KeyPair getKeyPair() throws NoSuchAlgorithmException { // creating the object of KeyPairGenerator KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); // initializing with 1024 kpg.initialize(1024); // returning the key pairs return kpg.genKeyPair(); } } |
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Output:
Signature:[-121, -82, .... .... ....104, 114, -67]
Example 2: To show InvalidKeyException
// Java program to demonstrate // initSign() method import java.security.*; import java.util.*; public class GFG1 { public static void main(String[] argv) throws Exception { try { // creating byte array object byte[] outbuff = new byte[1000]; // data to be updated byte[] data = "test".getBytes("UTF8"); // creating the object of Signature Signature sr = Signature.getInstance("SHA1WithRSA"); // creating the object of SecureRandom SecureRandom sb = SecureRandom.getInstance("SHA1PRNG"); // initializing the signature object with null key pair // for signing using initSign() method System.out.println("Trying to put the null as key"); sr.initSign(null, sb); // updating the data sr.update(data); // getting the signature byte // of an signing operation // by using method sign() byte[] bytes = sr.sign(); // pritning the number of byte System.out.println("Signature:" + Arrays.toString(bytes)); } catch (NoSuchAlgorithmException e) { System.out.println("Exception thrown : " + e); } catch (InvalidKeyException e) { System.out.println("Exception thrown : " + e); } } } |
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Output:
Trying to put the null as key Exception thrown : java.security.InvalidKeyException: Key must not be null
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