In RSA encryption, we encrypt sensitive information with a public key and a matching private key is used to decrypt the same. Let us first generate those keys programmatically in Java. You can also use this online RSA tool to generate these keys. We can use the factory method to generate these keys using KeyPairGenerator. Securely generate and store public/private keys on Android. Ask Question Asked 3 years. Share and store RSA - public key in java server and vice versa. When should I generate new public & private keys using RSA? Storing sensitive info in DB with Public/Private Asymmetric keys. Sending Private Keys, does it make sense?
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. In that case the program can import and use the private key for signing, as shown in Weaknesses and Alternatives.
In other cases the program needs to generate the key pair. A key pair is generated by using the
KeyPairGenerator class.
In this example you will generate a public/private key pair for the Digital Signature Algorithm (DSA). You will generate keys with a 1024-bit length.
Generating a key pair requires several steps:
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Create a Key Pair Generator
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The first step is to get a key-pair generator object for generating keys for the DSA signature algorithm.
As with all engine classes, the way to get a
KeyPairGenerator object for a particular type of algorithm is to call the getInstance static factory method on the KeyPairGenerator class. This method has two forms, both of which hava a String algorithm first argument; one form also has a String provider second argument.
A caller may thus optionally specify the name of a provider, which will guarantee that the implementation of the algorithm requested is from the named provider. The sample code of this lesson always specifies the default SUN provider built into the JDK.
Put the following statement after the
line in the file created in the previous step, Prepare Initial Program Structure:
Initialize the Key Pair Generator
The next step is to initialize the key pair generator. All key pair generators share the concepts of a keysize and a source of randomness. The
KeyPairGenerator class has an initialize method that takes these two types of arguments.
The keysize for a DSA key generator is the key length (in bits), which you will set to 1024.
Generate Rsa Key Command
The source of randomness must be an instance of the
SecureRandom class that provides a cryptographically strong random number generator (RNG). For more information about SecureRandom , see the SecureRandom API Specification and the Java Cryptography Architecture Reference Guide .
The following example requests an instance of
SecureRandom that uses the SHA1PRNG algorithm, as provided by the built-in SUN provider. The example then passes this SecureRandom instance to the key-pair generator initialization method.
Some situations require strong random values, such as when creating high-value and long-lived secrets like RSA public and private keys. To help guide applications in selecting a suitable strong
SecureRandom implementation, starting from JDK 8 Java distributions include a list of known strong SecureRandom implementations in the securerandom.strongAlgorithms property of the java.security.Security class. When you are creating such data, you should consider using SecureRandom.getInstanceStrong() , as it obtains an instance of the known strong algorithms.
Windows 7 home premium 32 product key generator. Generate the Pair of Keys
The final step is to generate the key pair and to store the keys in
PrivateKey and PublicKey objects.
You can encrypt given data using the Cipher class of the javax.crypto package. Follow the steps given below to encrypt given data using Java.
Step 1: Create a KeyPairGenerator objectGenerate Rsa Public Key
The KeyPairGenerator class provides getInstance() method which accepts a String variable representing the required key-generating algorithm and returns a KeyPairGenerator object that generates keys.
Create KeyPairGenerator object using the getInstance() method as shown below.
Step 2: Initialize the KeyPairGenerator object
The KeyPairGenerator class provides a method named initialize() this method is used to initialize the key pair generator. This method accepts an integer value representing the key size.
Generate Rsa Keys In Java
Initialize the KeyPairGenerator object created in the previous step using the initialize() method as shown below.
Step 3: Generate the KeyPairGenerator
You can generate the KeyPair using the generateKeyPair() method of the KeyPairGenerator class. Generate the key pair using this method as shown below.
Step 4: Get the public key
You can get the public key from the generated KeyPair object using the getPublic() method as shown below.
Get the public key using this method as shown below.
Step 5: Create a Cipher object
The getInstance() method of Cipher class accepts a String variable representing the required transformation and returns a Cipher object that implements the given transformation.
Create the Cipher object using the getInstance() method as shown below.
Step 6: Initialize the Cipher object
The init() method of the Cipher class accepts two parameters an integer parameter representing the operation mode (encrypt/decrypt) and, a Key object representing the public key.
Initialize the Cypher object using the init() method as shown below.
Step 7: Add data to the Cipher object
The update() method of the Cipher class accepts a byte array representing the data to be encrypted and updates the current object with the data given.
Update the initialized Cipher object by passing the data to the update() method in the form of byte array as shown below.
Step 8: Encrypt the data
The doFinal() method of the Cipher class completes the encryption operation. Therefore, finish the encryption using this method as shown below.
Example
Following Java program accepts text from user, encrypts it using RSA algorithm and, prints the encrypted format of the given text.
Output
The above program generates the following output −
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