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Nov 01, 2018 The code snippet below show you how to use the JDK Security API to generate public and private keys. A private key can be use to sign a document and the public key is use to verify that the signature of the document is valid. A separate public key file is not created at the same step though. To extract public key from the private key file into separate public key file you use your openssl rsa -in private.pem -pubout -out public.pem command. When you produce a public key this way, it is extracted from the private key file, not calculated. The -y option will read a private SSH key file and prints an SSH public key to stdout. The public key part is redirected to the file with the same name as the private key but with the.pub file extension. If the key has a password set, the password will be required to generate the public key. To check the details of the generated public key. Nov 10, 2011 4. Your public and private SSH key should now be generated. Open the file manager and navigate to the.ssh directory. You should see two files: idrsa and idrsa.pub. Upload the idrsa.pub file to the home folder of your remote host (assuming your remote host is running Linux as well). Connect to your remote host via SSH and use the following command to move the public key to the correct. Generating Keys for Encryption and Decryption.; 3 minutes to read +7; In this article. Creating and managing keys is an important part of the cryptographic process. Symmetric algorithms require the creation of a key and an initialization vector (IV). The key must be kept secret from anyone who should not decrypt your data.

1. Generating A Public Key From A Private Key Work
2. Generating Public Key From Private Key Openssl
3. Generating A Public Key From A Private Key West
4. Generating Public Key From Private Key

A lost SSH public-key or a web service generates an SSH key but does not provide the public-key part to you. What to do now? There is a solution for this situation.

When you have an SSH key you need the public key to setup SSH passwordless login with SSH-key. But if you have lost the public key part but still have the private key, there is a way to regenerate the key.

With the public key missing, the following command will show you that there is no public key for this SSH key.

The -l option instructs to show the fingerprint in the public key while the -f option specifies the file of the key to list the fingerprint for.

To generate the missing public key again from the private key, the following command will generate the public key of the private key provided with the -f option.

The -y option will read a private SSH key file and prints an SSH public key to stdout. The public key part is redirected to the file with the same name as the private key but with the .pub file extension. If the key has a password set, the password will be required to generate the public key.

To check the details of the generated public key execute the following command as shown above.

The output of this command shows the key size as the first column, the fingerprint as the second column and after the file name, the type is shown in brackets. In the example above, a 4096 bit RSA key.

Read more of my posts on my blog at http://blog.tinned-software.net/.

Several tools exist to generate SSH public/private key pairs. The following sections show how to generate an SSH key pair on UNIX, UNIX-like and Windows platforms.

Generating an SSH Key Pair on UNIX and UNIX-Like Platforms Using the ssh-keygen Utility

UNIX and UNIX-like platforms (including Solaris and Linux) include the ssh-keygen utility to generate SSH key pairs.

Generating A Public Key From A Private Key Work

1. Navigate to your home directory:
2. Run the ssh-keygen utility, providing as filename your choice of file name for the private key:

   The ssh-keygen utility prompts you for a passphrase for the private key.

3. Enter a passphrase for the private key, or press Enter to create a private key without a passphrase:

   Note:

   While a passphrase is not required, you should specify one as a security measure to protect the private key from unauthorized use. When you specify a passphrase, a user must enter the passphrase every time the private key is used.

   The ssh-keygen utility prompts you to enter the passphrase again.

4. Enter the passphrase again, or press Enter again to continue creating a private key without a passphrase:
5. The ssh-keygen utility displays a message indicating that the private key has been saved as filename and the public key has been saved as filename.pub. It also displays information about the key fingerprint and randomart image.

Generating Public Key From Private Key Openssl

Generating an SSH Key Pair on Windows Using the PuTTYgen Program

Generating A Public Key From A Private Key West

The PuTTYgen program is part of PuTTY, an open source networking client for the Windows platform.

Generating Public Key From Private Key

1. Download and install PuTTY or PuTTYgen.

   To download PuTTY or PuTTYgen, go to http://www.putty.org/ and click the You can download PuTTY here link.

2. Run the PuTTYgen program.
3. Set the Type of key to generate option to SSH-2 RSA.
4. In the Number of bits in a generated key box, enter 2048.
5. Click Generate to generate a public/private key pair.

   As the key is being generated, move the mouse around the blank area as directed.

6. (Optional) Enter a passphrase for the private key in the Key passphrase box and reenter it in the Confirm passphrase box.

   Note:

   While a passphrase is not required, you should specify one as a security measure to protect the private key from unauthorized use. When you specify a passphrase, a user must enter the passphrase every time the private key is used.

7. Click Save private key to save the private key to a file. To adhere to file-naming conventions, you should give the private key file an extension of .ppk (PuTTY private key).

   Note:

   The .ppk file extension indicates that the private key is in PuTTY's proprietary format. You must use a key of this format when using PuTTY as your SSH client. It cannot be used with other SSH client tools. Refer to the PuTTY documentation to convert a private key in this format to a different format.
8. Select all of the characters in the Public key for pasting into OpenSSH authorized_keys file box.

   Make sure you select all the characters, not just the ones you can see in the narrow window. If a scroll bar is next to the characters, you aren't seeing all the characters.

9. Right-click somewhere in the selected text and select Copy from the menu.
10. Open a text editor and paste the characters, just as you copied them. Start at the first character in the text editor, and do not insert any line breaks.
11. Save the text file in the same folder where you saved the private key, using the .pub extension to indicate that the file contains a public key.
12. If you or others are going to use an SSH client that requires the OpenSSH format for private keys (such as the ssh utility on Linux), export the private key:
    1. On the Conversions menu, choose Export OpenSSH key.
    2. Save the private key in OpenSSH format in the same folder where you saved the private key in .ppk format, using an extension such as .openssh to indicate the file's content.