1. Java Generate Public Private Key Rsa Download
2. Java Generate Rsa Private Key
3. Java Generate Public Private Key Pair
4. Generate Rsa Public Private Key
5. Java Generate Rsa Public Private Key Pair

JAVA generate RSA Public and Private Key Pairs using bouncy castle Crypto APIs. The following sample code generates RSA public and private keys and save them in separate files. You can pass the file names as input parameters and the program generates keys with 1024-bit size. Jan 24, 2017 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. Distribute the public key to whoever needs it but safely secure the private key. Generating RSA Public Private Key We can use factory method to generate these keys using KeyPairGenerator. For the demo purpose we are using a key size of 1024. By default, the private key is generated in PKCS#8 format and the public key is generated in X.509 format. The most popular Public Key Algorithms are RSA, Diffie-Hellman, ElGamal, DSS. Generate a Public-Private Key Pair. There are several ways to generate a Public-Private Key Pair depending on your platform. In this example, we will create a pair using Java. The Cryptographic Algorithm we will use in this example is RSA.

• Generate Public and Private Keys In order to be able to create a digital signature, you need a private key. (Its corresponding public key will be needed in order to verify the authenticity of the signature.) In some cases the key pair (private key and corresponding public key) are already available in files.
• Nov 01, 2018 A private key can be use to sign a document and the public key is use to verify that the signature of the document is valid. The API we use to generate the key pairs is in the java.security package. That’s mean we have to import this package into our code.

Contents

• 3. Saving the Keys in Binary Format
• Source Code

1. Introduction

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. Distribute the public key to whoever needs it but safely secure the private key.

Public key cryptography can be used in two modes:

Encryption: Only the private key can decrypt the data encrypted with the public key.

Authentication: Data encrypted with the private key can only be decrypted with the public key thus proving who the data came from.

2. Generating a Key Pair

First step in creating an RSA Key Pair is to create a KeyPairGeneratorfrom a factory method by specifying the algorithm (“RSA” in this instance):

Initialize the KeyPairGenerator with the key size. Use a key size of 1024 or 2048. Currently recommended key size for SSL certificates used in e-commerce is 2048 so that is what we use here.

From the KeyPair object, get the public key using getPublic() and the private key using getPrivate().

3. Saving the Keys in Binary Format

Save the keys to hard disk once they are obtained. This allows re-using the keys for encryption, decryption and authentication.

What is the format of the saved files? The key information is encoded in different formats for different types of keys. Here is how you can find what format the key was saved in. On my machine, the private key was saved in PKCS#8 format and the public key in X.509 format. We need this information below to load the keys.

3.1. Load Private Key from File

After saving the private key to a file (or a database), you might need to load it at a later time. You can do that using the following code. Note that you need to know what format the data was saved in: PKCS#8 in our case.

3.2 Load Public Key from File

Load the public key from a file as follows. The public key has been saved in X.509 format so we use the X509EncodedKeySpec class to convert it.

4. Use Base64 for Saving Keys as Text

Save the keys in text format by encoding the data in Base64. Java 8 provides a Base64 class which can be used for the purpose. Save the private key with a comment as follows:

And the public key too (with a comment):

Java Generate Public Private Key Rsa Download

5. Generating a Digital Signature

As mentioned above, one of the purposes of public key cryptography is digital signature i.e. you generate a digital signature from a file contents, sign it with your private key and send the signature along with the file. The recipient can then use your public key to verify that the signature matches the file contents.

Here is how you can do it. Use the signature algorithm “SHA256withRSA” which is guaranteed to be supported on all JVMs. Use the private key (either generated or load from file as shown above) to initialize the Signatureobject for signing. It is then updated with contents from the data file and the signature is generated and written to the output file. This output file contains the digital signature and must be sent to the recipient for verification.

Java Generate Rsa Private Key

6. Verifying the Digital Signature

The recipient uses the digital signature sent with a data file to verify that the data file has not been tampered with. It requires access to the sender’s public key and can be loaded from a file if necessary as presented above.

Java Generate Public Private Key Pair

The code below updates the Signature object with data from the data file. It then loads the signature from file and uses Signature.verify() to check if the signature is valid.

And that in a nutshell is how you can use RSA public and private keys for digital signature and verification.

Source Code

Go here for the source code.

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Generate Rsa Public Private Key

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Java Generate Rsa Public Private Key Pair