How to create .jks file for Flangapp - SAAS Online app builder from website

First, download keystore explorer. Link: https://keystore-explorer.org/​

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Step 1: Create a keystore and key pair​

1. Start KeyStore Explorer.
2. Choose Create a new KeyStore.
3. From New KeyStore Type, choose JKS.
4. Click OK.
   
   
5. Generate a key pair:
   1. Select Tools > Generate Key Pair.
   2. In Generate Key Pair,choose the following algorithm selection options:
      • RSA
      • Key Size: 4096
        
        
   3. Click OK.
      Generating Key Pair dialog appears, then disappears after a key is generated.
   4. From Generate Key Pair Certificate, click the Edit name icon
      
      .
   5. Complete the Namefields:
      • For the Common Name (CN) use the Fully Qualified Domain Name (FQDN) of your server.
        
        
   6. Click OK.
   7. Specify the domain name of your server as an alternative name. Click Add Extensions, click the + icon, and select Subject Alternative Name.
   8. In the Subject Alternative Name Extension dialog, click the + icon, select DNS Name, and in General Name Value type the domain name of your server.
   9. Click OK until you return to the Generate Key Pair Certificate dialog.
   10. In Generate Key Pair Certificate, click OK.
   11. In New Key Pair Entry Alias, enter an alias for the key pair.
       The alias is pre-set to the CN set in the Name dialog.
   12. Click OK.
   13. In New Key Pair Entry Password, enter a password, and click OK.
       The Generate Key Pair dialog displays "Key Pair Generation Successful".

1. Click OK.
   The new key pair is displayed in the KeyStore Explorer window.
   
   
2. Save the keystore:
   1. From the KeyStore Explorer menu, select File > Save.
      The Set KeyStore Password dialog appears.
   2. Enter a password for the keystore. This password must be the same as the password for the key pair generated in step 5 above.
   3. Click OK.
      The Save KeyStore As dialog appears.
   4. Enter the name of the keystore.
      This format is suggested for easy identification of your keystores: fqdn_domain_com.jks
   5. Click Save.
      Your keystore file is saved to your computer.

Step 2: Generate and send certificate signature request​

1. Right-click the key pair entry.
2. Choose Generate CSR.
   The Generate CSR dialog appears.
   
   
3. (Optional) Enter additional values.
4. Click OK.
   The CSR Generation Successful dialog appears.
5. Click OK.
6. Send the generated CSR file to your certificate authority.

Step 3: Import signed certificates to your keystore​

1. When the certificate authority returns your signed certificate and key, place them in a directory accessible by Keystore Explorer.
2. In Keystore Explorer, right-click the same key pair entry used to generate the CSR and choose Import CA Reply > From File.
3. Select the signed certificate from your certificate authority, and click Import.
   The signed certificate is added to the key pair entry as the server-level certificate.
4. To verify the certificate chain, right-click the key pair entry, and choose View Details > Certificate Chain Details.
5. If you need to import intermediate and root-level certificates, right-click the key pair entry, and choose Edit Certificate Chain > Append Certificate to append the intermediate and root-level certificates. See Append certificates to an existing keystore, below.
6. From the menu bar, select File > Save to save the imported certificate to your keystore.