Digital Signature in PKCS 7 format with base 64 encoding

Hi,

I have a requirement from client

Digital Signature in PKCS 7 format with base 64 encoding

.

Process is that we will send a url with some parameter values and a digital signature of that parameter values.

I am trying with this code.

package tester;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import java.security.KeyPairGenerator;
import javax.crypto.KeyGenerator;
public class SignFile 
{
         private PrivateKey priv_key;
         private byte[] file_content;
         private MessageDigest messageDigest;
         private Cipher cipher;
         private byte[] sign;
         private byte[] encrypted_sign;
        
         public SignFile(byte[] content)
        {
	this.file_content=content;
        }
        
        public SignFile(PrivateKey key,byte[] content)
       {
               this.priv_key=key;
               this.file_content=content;
       }

public byte[] signFile(byte[] b) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException
      {
	messageDigest = MessageDigest.getInstance("MD5");
                messageDigest.update( b );
                sign= messageDigest.digest();
             
               // get an RSA cipher 
               //cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
               //cipher = Cipher.getInstance("Blowfish/ECB/PKCS5Padding");
           
                try
               {
                          	cipher = Cipher.getInstance("Blowfish/ECB/PKCS5Padding");
                                //cipher = Cipher.getInstance("AES/ECB/PKCS7Padding");

}
               catch(Exception e)
              {
	                System.out.println("exception cipher getinstance>>"+e);
              }
             // encrypt the message digest with the RSA private key
             // to create the signature
             KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("Blowfish");
             KeyPair p_key1 = keyPairGenerator.generateKeyPair();
             PrivateKey p_key = (PrivateKey) p_key1.getPrivate();
             cipher.init(Cipher.ENCRYPT_MODE, p_key);
             encrypted_sign= cipher.doFinal(sign);

return encrypted_sign;
       }
       public static void main(String[] args) 
       {
	String ss = "this is just for test";
	byte[] b = ss.getBytes();
	System.out.println("Byte Value>>"+b);
 	SignFile sFile = new SignFile(b);
 	try
 	{
 		b = sFile.signFile(b);
 	}catch(Exception e){
 		System.out.println("Exception >>"+e);
 	}
 	System.out.println("Digital Signature Value>>"+b);
      }
}

Queries:

1. Who is the service provider for PKCS 7 format and how I should integrate?
2. Is .JKS, .CER and .KEY required for my requirement.
If this files needed, how I should start.

Please give me suggestions for this requirement.