Java Read Public Key Generate Private Key
Generate a 2048-bit RSA private key. $ openssl genrsa -out privatekey.pem 2048. Convert private Key to PKCS#8 format (so Java can read it) $ openssl pkcs8 -topk8 -inform PEM -outform DER -in privatekey.pem -out privatekey.der -nocrypt. Output public key portion in DER format (so Java can read. This definitely was useful. In my case I was trying to use my openssh pubkey and had to run this magic first: ssh-keygen -f /.ssh/idrsa.pub -e -m pkcs8 key.pkcs8 - apparently openssh uses a proprietary format for the public key and and the standard pkcs8 format for the private. Next, VerSig needs to import the encoded public key bytes from the file specified as the first command line argument and to convert them to a PublicKey.A PublicKey is needed because that is what the Signature initVerify method requires in order to initialize the Signature object for verification.
Java Key Code
Oct 21, 2016 Create and read PKCS #8 format private key in java program. In this short article I will show you how to store private key in pkcs8 format in java and again read back the stored key in java. PKCS #8 defines a standard syntax for storing private key information. Oct 08, 2010 The signature is obtained by signing the Certificate with a CA private key but to verify the sgnature i require the public key which is present in the same.crt file. I am not clear how to generate the public key for verifying the signature. How this can be done in java is my question.
Press generate and follow instructions to generate (public/private) key pair. Create a new 'authorizedkeys' file (with Notepad): Copy your public key data from the 'Public key for pasting into OpenSSH authorizedkeys file' section of the PuTTY Key Generator, and paste the key data to the 'authorizedkeys' file. Public Keys, Private Keys, and Certificates. When performing authentication, SSL uses a technique called public-key cryptography. Public-key cryptography is based on the concept of a key pair, which consists of a public key and a private key.Data that has been encrypted with a public key can be decrypted only with the corresponding private key.
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.
Java Read Public Key Generate Private Keys
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.
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 PrivateKey and PublicKey objects.
Next, VerSig needs to import the encoded public key bytes from the file specified as the first command line argument and to convert them to a PublicKey. A PublicKey is needed because that is what the SignatureinitVerify method requires in order to initialize the Signature object for verification.
First, read in the encoded public key bytes.
Now the byte array encKey contains the encoded public key bytes.
You can use a KeyFactory class in order to instantiate a DSA public key from its encoding. The KeyFactory class provides conversions between opaque keys (of type Key) and key specifications, which are transparent representations of the underlying key material. With an opaque key you can obtain the algorithm name, format name, and encoded key bytes, but not the key material, which, for example, may consist of the key itself and the algorithm parameters used to calculate the key. (Note that PublicKey, because it extends Key, is itself a Key.)
So, first you need a key specification. You can obtain one via the following, assuming that the key was encoded according to the X.509 standard, which is the case, for example, if the key was generated with the built-in DSA key-pair generator supplied by the SUN provider:
Now you need a KeyFactory object to do the conversion. That object must be one that works with DSA keys.
Finally, you can use the KeyFactory object to generate a PublicKey from the key specification.