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:
I would like to create a map that will generate random data( it will generate a random value for each key). I have thought deeply about it but can't get a right answer. I know the sizes for t. Nor are there any bits that have a specific meaning as in (3)DES parity bits. So generating a key can be as simple as generating a byte array with random values, and creating a SecretKeySpec around it. But there are still advantages to the method you are using: the KeyGenerator is specifically created to generate keys. This means that the code may be optimized for this generation. Stream generate method in Java with examples; Which Java libraries are useful for competitive programming? Extract all integers from the given string in Java; Integer.MAXVALUE and Integer.MINVALUE in Java with Examples; HashMap getOrDefault(key, defaultValue) method in Java with Examples; How to calculate log base 2 of an Integer in Java? Key generators are constructed using one of the getInstance class methods of this class. KeyGenerator objects are reusable, i.e., after a key has been generated, the same KeyGenerator object can be re-used to generate further keys. There are two ways to generate a key: in an algorithm-independent manner. Java KeyGenerator. The Java KeyGenerator class (javax.crypto.KeyGenerator) is used to generate symmetric encryption keys. A symmetric encryption key is a key that is used for both encryption and decryption of data, by a symmetric encryption algorithm.
Asymmetric algorithms require the creation of a public key and a private key. The public key can be made public to anyone, while the private key must known only by the party who will decrypt the data encrypted with the public key. This section describes how to generate and manage keys for both symmetric and asymmetric algorithms. Symmetric Keys.
Create a Key Pair Generator
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 KeyPairGeneratorWondows phone generate recovery key. 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.
Java Random Number Generator Example
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.
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.
Generate the Pair of Keys
The final step is to generate the key pair and to store the keys in PrivateKey and PublicKey objects.
The Java KeyGenerator class (javax.crypto.KeyGenerator) is used to generate symmetric encryption keys. A symmetric encryption key is a key that is used for both encryption and decryption of data, by a symmetric encryption algorithm. In this Java KeyGenerator tutorial I will show you how to generate symmetric encryption keys.
Creating a KeyGenerator Instance
Before you can use the Java KeyGenerator class you must create a KeyGenerator instance. You create a KeyGenerator instance by calling the static method getInstance() passing as parameter the name of the encryption algorithm to create a key for. Here is an example of creating a Java KeyGenerator instance:
This example creates a KeyGenerator instance which can generate keys for the AES encryption algorithm.
Initializing the KeyGenerator
After creating the KeyGenerator instance you must initialize it. Initializing a KeyGenerator instance is done by calling its init() method. Here is an example of initializing a KeyGenerator instance:
The KeyGeneratorinit() method takes two parameters: The bit size of the keys to generate, and a SecureRandom that is used during key generation.
Generating a Key
Once the Java KeyGenerator instance is initialized you can use it to generate keys. Generating a key is done by calling the KeyGeneratorgenerateKey() method. Here is an example of generating a symmetric key: