Generating Rsa Key And Signing Java

23.05.202023.05.2020

Now that you have created a public key and a private key, you are ready to sign the data. In this example you will sign the data contained in a file. GenSig gets the file name from the command line. A digital signature is created (or verified) using an instance of the Signature class.

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Rsa Java Code
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Generating Rsa Key And Signing Java Code

Signing data, generating a digital signature for that data, is done with the following steps.

Get a Signature Object: The following gets a Signature object for generating or verifying signatures using the DSA algorithm, the same algorithm for which the program generated keys in the previous step, Generate Public and Private Keys.

Note: When specifying the signature algorithm name, you should also include the name of the message digest algorithm used by the signature algorithm. SHA1withDSA is a way of specifying the DSA signature algorithm, using the SHA-1 message digest algorithm.

Short Answer: NO, it is not safe, do NOT do this. Longer Answer: You are true that you can use your RSA keypair for both operations.This approach is used in many applications and scenarios. There are Web Services or Single Sign-On implementations, which enforce you to use the same key. Jan 24, 2017 Let us learn the basics of generating and using RSA keys in Java. Java provides classes for the generation of RSA public and private key pairs with the package java.security. You can use RSA keys pairs in public key cryptography. Public key cryptography uses a pair of keys for encryption. This lesson demonstrates the use of the JDK Security API with respect to signing documents. The lesson shows what one program, executed by the person who has the original document, would do to generate keys, generate a digital signature for the document using the private key, and export the public key and the signature to files. SSL Certificate CSR Creation for Java Based Web Servers. If you already have your SSL Certificate and just need to install it, see SSL Certificate Installation:: Java Web Servers. How to generate a CSR using Java Keytool.NOTE: You must generate a new keystore through this process. Usage Guide - RSA Encryption and Decryption Online. In the first section of this tool, you can generate public or private keys. To do so, select the RSA key size among 515, 1024, 2048 and 4096 bit click on the button. This will generate the keys for you. We’re interested in function #2 above. This is a beginner tutorial on how to generate a pair of public/private RSA keys, use the private key to sign a message using Python 2 on Ubuntu 14.04, and then later use the public key to verify the message using C# and.NET 4 on Windows 10. Disclaimer: I’m not a cryptography or security expert.

I have previously used the provider SunRsaSign for generating an RSA key pair that was used for signing data. But I am not sure if it is safe or if it makes sense to use a key pair generated by SunRsaSign for encrypting data. I have noticed that the provider SunJSSE contains: sun.security.rsa.RSAKeyPairGenerator.

Initialize the Signature Object

Before a Signature object can be used for signing or verifying, it must be initialized. The initialization method for signing requires a private key. Use the private key placed into the PrivateKey object named priv in the previous step.

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Supply the Signature Object the Data to Be Signed This program will use the data from the file whose name is specified as the first (and only) command line argument. The program will read in the data a buffer at a time and will supply it to the Signature object by calling the update method.

Generate the Signature

Once all of the data has been supplied to the Signature object, you can generate the digital signature of that data.

Example of RSA generation, sign, verify, encryption, decryption and keystores in Java

RsaExample.java

Rsa Java Code

importjavax.crypto.Cipher;

importjava.io.InputStream;

importjava.security.*;

importjava.util.Base64;

import staticjava.nio.charset.StandardCharsets.UTF_8;

publicclassRsaExample {

publicstaticKeyPairgenerateKeyPair() throwsException {

KeyPairGenerator generator =KeyPairGenerator.getInstance('RSA');

generator.initialize(2048, newSecureRandom());

KeyPair pair = generator.generateKeyPair();

return pair;

}

publicstaticKeyPairgetKeyPairFromKeyStore() throwsException {

//Generated with:

// keytool -genkeypair -alias mykey -storepass s3cr3t -keypass s3cr3t -keyalg RSA -keystore keystore.jks

InputStream ins =RsaExample.class.getResourceAsStream('/keystore.jks');

KeyStore keyStore =KeyStore.getInstance('JCEKS');

keyStore.load(ins, 's3cr3t'.toCharArray()); //Keystore password

KeyStore.PasswordProtection keyPassword =//Key password

newKeyStore.PasswordProtection('s3cr3t'.toCharArray());

KeyStore.PrivateKeyEntry privateKeyEntry = (KeyStore.PrivateKeyEntry) keyStore.getEntry('mykey', keyPassword);

java.security.cert.Certificate cert = keyStore.getCertificate('mykey');

PublicKey publicKey = cert.getPublicKey();

PrivateKey privateKey = privateKeyEntry.getPrivateKey();

returnnewKeyPair(publicKey, privateKey);

}

publicstaticStringencrypt(StringplainText, PublicKeypublicKey) throwsException {

Cipher encryptCipher =Cipher.getInstance('RSA');

encryptCipher.init(Cipher.ENCRYPT_MODE, publicKey);

byte[] cipherText = encryptCipher.doFinal(plainText.getBytes(UTF_8));

returnBase64.getEncoder().encodeToString(cipherText);

}

publicstaticStringdecrypt(StringcipherText, PrivateKeyprivateKey) throwsException {

byte[] bytes =Base64.getDecoder().decode(cipherText);

Cipher decriptCipher =Cipher.getInstance('RSA');

decriptCipher.init(Cipher.DECRYPT_MODE, privateKey);

returnnewString(decriptCipher.doFinal(bytes), UTF_8);

}

publicstaticStringsign(StringplainText, PrivateKeyprivateKey) throwsException {

Signature privateSignature =Signature.getInstance('SHA256withRSA');

privateSignature.initSign(privateKey);

privateSignature.update(plainText.getBytes(UTF_8));

byte[] signature = privateSignature.sign();

returnBase64.getEncoder().encodeToString(signature);

}

publicstaticbooleanverify(StringplainText, Stringsignature, PublicKeypublicKey) throwsException {

Signature publicSignature =Signature.getInstance('SHA256withRSA');

publicSignature.initVerify(publicKey);

publicSignature.update(plainText.getBytes(UTF_8));

byte[] signatureBytes =Base64.getDecoder().decode(signature);

return publicSignature.verify(signatureBytes);

}

publicstaticvoidmain(String.. argv) throwsException {

//First generate a public/private key pair

KeyPair pair = generateKeyPair();

//KeyPair pair = getKeyPairFromKeyStore();

//Our secret message

String message ='the answer to life the universe and everything';

//Encrypt the message

String cipherText = encrypt(message, pair.getPublic());

//Now decrypt it

String decipheredMessage = decrypt(cipherText, pair.getPrivate());

System.out.println(decipheredMessage);

//Let's sign our message

String signature = sign('foobar', pair.getPrivate());

//Let's check the signature

boolean isCorrect = verify('foobar', signature, pair.getPublic());

System.out.println('Signature correct: '+ isCorrect);

}

commented Oct 17, 2019

It's good thank you so much , How can i create base64 like jwt (header,body,sign) ?

commented Nov 26, 2019

Thanks for the code. One issue - using openjdk version '11.0.5-ea' 2019-10-15 requires the KeyStore.getInstance('JCEKS') code to be KeyStore.getInstance('PKCS12').

commented Dec 29, 2019