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.)
We will start by learning how to generate OpenPGP-compliant keys using Java. Before we can encrypt, we must generate our encryption key pair: one public, one private. A PGP key ring keeps your keys together. We normally want two key rings. One stores our public keys and the public keys of whoever we trust and exchange messages with. This chapter demonstrates how to generate an RSA based OpenPGP key pair with OpenPGP Library for Java. When we create an OpenPGP key pair, a few parameters must be passed. These include: Encryption key size in bytes (recommended between 1024 and 3072) User ID. Key algorithm (RSA or ELGAMAL) private key password. 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. The KeyPairGenerator class is used to generate pairs of public and private keys. Key pair generators are constructed using the getInstance factory methods (static methods that return instances of a given class). A Key pair generator for a particular algorithm creates a public/private key pair that can be used with this algorithm.
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:
Create a Key Pair Generator
The first step is to get a key-pair generator object for generating keys for the DSA signature algorithm.
![Pgp Pgp](/uploads/1/2/5/8/125876498/648599651.png)
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.
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
The KeyPairGenerator class is used to generate pairs of public and private keys. Key pair generators are constructed using the PrivateKey
and PublicKey
objects.getInstance
factory methods (static methods that return instances of a given class). Generate Pgp Key Windows
A Key pair generator for a particular algorithm creates a public/private key pair that can be used with this algorithm. It also associates algorithm-specific parameters with each of the generated keys.
There are two ways to generate a key pair: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:
Java Generate Pgp Key Pair System
![Java Generate Pgp Key Pair Java Generate Pgp Key Pair](/uploads/1/2/5/8/125876498/677234065.jpg)
- Algorithm-Independent InitializationAll key pair generators share the concepts of a keysize and a source of randomness. The keysize is interpreted differently for different algorithms (e.g., in the case of the DSA algorithm, the keysize corresponds to the length of the modulus). There is an
initialize
method in this KeyPairGenerator class that takes these two universally shared types of arguments. There is also one that takes just akeysize
argument, and uses theSecureRandom
implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation ofSecureRandom
, a system-provided source of randomness is used.)Since no other parameters are specified when you call the above algorithm-independentinitialize
methods, it is up to the provider what to do about the algorithm-specific parameters (if any) to be associated with each of the keys.If the algorithm is the DSA algorithm, and the keysize (modulus size) is 512, 768, or 1024, then the Sun provider uses a set of precomputed values for thep
,q
, andg
parameters. If the modulus size is not one of the above values, the Sun provider creates a new set of parameters. Other providers might have precomputed parameter sets for more than just the three modulus sizes mentioned above. Still others might not have a list of precomputed parameters at all and instead always create new parameter sets. - Algorithm-Specific InitializationFor situations where a set of algorithm-specific parameters already exists (e.g., so-called community parameters in DSA), there are two
initialize
methods that have anAlgorithmParameterSpec
argument. One also has aSecureRandom
argument, while the the other uses theSecureRandom
implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation ofSecureRandom
, a system-provided source of randomness is used.)
In case the client does not explicitly initialize the KeyPairGenerator (via a call to an
initialize
method), each provider must supply (and document) a default initialization. For example, the Sun provider uses a default modulus size (keysize) of 1024 bits. Note that this class is abstract and extends from
KeyPairGeneratorSpi
for historical reasons. Application developers should only take notice of the methods defined in this KeyPairGenerator
class; all the methods in the superclass are intended for cryptographic service providers who wish to supply their own implementations of key pair generators. Every implementation of the Java platform is required to support the following standard
KeyPairGenerator
algorithms and keysizes in parentheses: Generate Pgp Key Pair
- DiffieHellman (1024)
- DSA (1024)
- RSA (1024, 2048)