Java Generate Public Key From File
This lesson walks you through the steps necessary to use the JDK Security API to generate a digital signature for data and to verify that a signature is authentic. This lesson is meant for developers who wish to incorporate security functionality into their programs, including cryptography services.
The.pub file is your public key, and the other file is your private key. If you don’t have these files (or you don’t even have a.ssh directory), you can create them by running a program called ssh-keygen, which is provided with the SSH package on Linux/Mac systems and comes with the MSysGit package on Windows. I want to know if there is a way to create.key file for (public and private key) using keytool, I understand that we can generate a keystore using below command keytool -genkeypair -keysize 2048.
Generate a private-public key pair using keytool. Make and filter the log file into a html file. Protect your existing private rsa key with a passphrase. Save/Load Private and Public Key to/from a file / Published in: Java. Save to your folder(s). Copy this code and paste it in your HTML. Package net.java.edem; import. This lesson demonstrates the use of the JDK Security API with respect to signing documents. The lesson shows what one program, executed by the person who has the original document, would do to generate keys, generate a digital signature for the document using the private key, and export the public key and the signature to files. 2019-11-12 I want to know if there is a way to create.key file for (public and private key) using keytool, I understand that we can generate a keystore using below command keytool -genkeypair -keysize 2048. 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. The first step in configuring a VT Display session for SSH client authentication using a public key is to use the keytool program to generate a public-private key pair. About keytool keytool is a multipurpose utility program, included in the Java 2 Version 1.4 JRE and distributed with Host On-Demand, for managing keys and certificates.
This lesson demonstrates the use of the JDK Security API with respect to signing documents. The lesson shows what one program, executed by the person who has the original document, would do to generate keys, generate a digital signature for the document using the private key, and export the public key and the signature to files.
Then it shows an example of another program, executed by the receiver of the document, signature, and public key. It shows how the program could import the public key and verify the authenticity of the signature. The lesson also discusses and demonstrates possible alternative approaches and methods of supplying and importing keys, including in certificates.
For further information about the concepts and terminology (digital signatures, certificates, keystores), see the API and Tools Use for Secure Code and File Exchanges lesson.
In this lesson you create two basic applications, one for the digital signature generation and the other for the verification. This is followed by a discussion and demonstration of potential enhancements. The lesson contains three sections.
Generating a Digital Signature shows using the API to generate keys and a digital signature for data using the private key and to export the public key and the signature to files. The application gets the data file name from the command line.
Verifying a Digital Signature shows using the API to import a public key and a signature that is alleged to be the signature of a specified data file and to verify the authenticity of the signature. The data, public key, and signature file names are specified on the command line.
Weaknesses and Alternatives discusses potential weaknesses of the approach used by the basic programs. It then presents and demonstrates possible alternative approaches and methods of supplying and importing keys, including the use of files containing encoded key bytes and the use of certificates containing public keys.
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):
The default algorithm is RSA 2048.You are done. Your public key will be saved to the idrsa.pub file, by default it is C:usersyour user name.sshidrsa.pub. Finally, you will see the fingerprint for your key and SHA256. Generate a ssh key windows 1 download. You can just hit the Enter key to skip it.
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):
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.
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.
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.
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Source Code
Java Generate Public Key From File Taxes
Go here for the source code.