Java encryption and decryption and the operation of digital certificates

1 Java program to implement the maintenance of key repository
1.1 Java program lists all key library entries

Import java.util.*;  
Import java.io.*;  
Import java.security.*;  
public class showalias{public  
    static void Main (String args[]) throws exception{  
        String pass= "080302";  
        String name= ". KeyStore";  
        FileInputStream in=new FileInputStream (name);  
        KeyStore ks=keystore.getinstance ("JKS");             
        Ks.load (In,pass.tochararray ());  
        Enumeratione=ks.aliases ();  
        while (E.hasmoreelements ()) {  
            System.out.println (e.nextelement ());  
        }  
}}    

1.2 Java program to modify KeyStore password

Import java.io.*;  
Import java.security.*;  
public class setstorepass{public  
    static void Main (String args[]) throws exception{  
        char[] oldpass= "080302". ToC Hararray ();  
        Char[] newpass= "123456". ToCharArray ();  
        String name= ". KeyStore";  
        FileInputStream in=new FileInputStream (name);  
        KeyStore ks=keystore.getinstance ("JKS");  
        Ks.load (in,oldpass);  
        In.close ();  
        FileOutputStream output=new FileOutputStream (name);  
        Ks.store (output,newpass);  
        Output.close ();   
    }  
    

1.3 Java program to modify password and add entry for KeyStore entry

Package test;  
Import java.io.*;  
Import java.security.*;  
Import Java.security.cert.Certificate; public class setkeypass{public static void Main (String args[]) throws exception{//Read correlation parameter S    
        Tring name= ". KeyStore";    
        String alias= "MyKey";    
        Char[] storepass= "123456". ToCharArray ();   
        Char[] oldkeypass= "080302". ToCharArray ();    
        Char[] newkeypass= "123456". ToCharArray ();   
        Gets the KeyStore object of the KeyStore. KeyStore and loads the KeyStore fileinputstream in=new fileinputstream (name);   
        KeyStore ks=keystore.getinstance ("JKS");    
        Ks.load (In,storepass);   
        Gets the certificate chain certificate[] Cchain=ks.getcertificatechain (alias) for the corresponding entry for the alias;    
        Read the private key of the entry for the alias Privatekey pk= (Privatekey) Ks.getkey (Alias,oldkeypass);    
        Add a new entry to the KeyStore ks.setkeyentry (Alias,pk,newkeypass,cchain);    
        In.close (); Writes the contents of the KeyStore object to the new file FileOutputStream output=newFileOutputStream ("333");    
        Ks.store (Output,storepass);    
    Output.close ();  
 }    
}

1.4 Java Program Check alias and delete entry

Package test;  
Import java.io.*;  
Import java.security.*;  
public class deletealias{public  
    static void main (string args[]) throws exception{  
        String pass = "123456";  
        String name = ". KeyStore";  
        String alias = "MyKey";  
        FileInputStream in=new FileInputStream (name);  
        KeyStore ks=keystore.getinstance ("JKS");             
        Ks.load (In,pass.tochararray ());  
        if (Ks.containsalias (alias)) {  
            ks.deleteentry (alias);  
            FileOutputStream output=new FileOutputStream (name);   
            Ks.store (Output,pass.tochararray ());   
            System.out.println ("Alias" +alias+ "deleted");   
        } else{   
            System.out.println ("Alias not Exist");}}  
    

2 Java programs read certificates and display certificate designation information
2.1 Java program read certificate from certificate file

Import java.io.*;  
Import java.security.cert.*;  
public class printcert{public  
static void Main (String args[]) throws exception{  
        certificatefactory cf= Certificatefactory.getinstance ("X.509");  
        FileInputStream in=new FileInputStream ("My.cer");  
        Certificate c=cf.generatecertificate (in);    
        In.close ();    
        String s=c.tostring ();    
        Display certificate    
        fileoutputstream fout=new fileoutputstream ("Tmp.txt");    
         BufferedWriter out= New BufferedWriter (New OutputStreamWriter (Fout));    
        Out.write (S,0,s.length ());     
        Out.close ();      
}  
    

2.2 Java programs read certificates directly from KeyStore

Import java.io.*;  
Import java.security.*;  
Import java.security.cert.Certificate;  
public class printcert2{public  
    static void Main (String args[]) throws exception{   
          String pass= "080302";   
          String alias= "MyKey";   
          String name= ". KeyStore";   
          FileInputStream in=new FileInputStream (name);    
          KeyStore ks=keystore.getinstance ("JKS");              
          Ks.load (In,pass.tochararray ());   
          Certificate C=ks.getcertificate (alias);  
          In.close ();   
         System.out.println (C.tostring ());   
    }  
    

2.3 Java Program displays certificate designation information (full name/public key/signature, etc.)

Import java.io.*;  
Import java.security.*;  
Import java.security.cert.*;    
Import java.math.*;  public class showcertinfo{public static void Main (String args[]) throws exception{Certificatefactory    
        Cf=certificatefactory.getinstance ("X.509");    
        FileInputStream in=new FileInputStream ("My.cer");  
        Java.security.cert.Certificate c=cf.generatecertificate (in);  
        In.close ();    
        X509Certificate t= (X509Certificate) C;    
        SYSTEM.OUT.PRINTLN ("Version number" +t.getversion ());    
        SYSTEM.OUT.PRINTLN ("Serial number" +t.getserialnumber (). toString (16));   
        System.out.println ("Full Name" +t.getsubjectdn ());    
        System.out.println ("Issuer full name n" +t.getissuerdn ());  
        System.out.println ("Expiry date" +t.getnotbefore ());  
        System.out.println ("Expiry date" +t.getnotafter ());   
        SYSTEM.OUT.PRINTLN ("Signature Algorithm" +t.getsigalgname ());   
        Byte[] Sig=t.getsignature (); System.out.println ("Signature n" +new BigInteger (SIG). ToString (16));  
        PublicKey Pk=t.getpublickey ();   
        Byte[] pkenc=pk.getencoded ();   
        SYSTEM.OUT.PRINTLN ("Public Key");   
        for (int i=0;i< div= "" > System.out.print (pkenc[i]+ ",");  
 }    
}  
}

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