import java.math.BigInteger ;
import java.util.* ;
import java.io.* ;
import java.sql.*;

/**
 * Class for RSA Algorithm (RSA.java).
 *
 * Generates Prime numbers and Public/Private Keys. Performs Encryption and Decryption.
 *
 * @author  Chue Wai Lian
 * @version
 *
 * 1.0.0	11 Apr 2001
 * <br>		1st release.
 */
public class RSA
{
	/**
	 * Bit length of each prime number.
	 */
	int primeSize ;
            
	/**
	 * Two distinct large prime numbers p and q.
	 */
	BigInteger p, q ;

	/**
	 * Modulus N.
	 */
	BigInteger N ;

	/**
	 * r = ( p - 1 ) * ( q - 1 )
	 */
	BigInteger r ;

	/**
	 * Public exponent E and Private exponent D
	 */
	BigInteger E, D ;
static PrintStream pr;
static FileOutputStream out; 

public RSA() throws Exception{

out = new FileOutputStream("/assign/stats",true);
            pr=new PrintStream(out);
}

	/**
	 * Constructor.
	 *
	 * @param	primeSize		Bit length of each prime number.
	 */
	public RSA( int primeSize ) throws Exception
	{
out = new FileOutputStream("/assign/stats",true);
            pr=new PrintStream(out);
		this.primeSize = primeSize ;
System.out.println("primesize is : "+this.primeSize);
		// Generate two distinct large prime numbers p and q.
		long starttime=getCurrentTime();
generatePrimeNumbers() ;

		// Generate Public and Private Keys.
                
		generatePublicPrivateKeys() ;
                long endtime=getCurrentTime();
                System.out.println("Total time taken for key generation is  "+(endtime-starttime));
	pr.println("Time taken for key generation of "+primeSize+" bit key is :"+ (endtime-starttime));
       
        }
        public RSA(int primeSize,int probability){
        
        this.primeSize=primeSize;
        System.out.println("primesize is : "+this.primeSize);
        long starttime=getCurrentTime();
generatePrimeNumbers(probability) ;
generatePublicPrivateKeys() ;
                long endtime=getCurrentTime();
                System.out.println("Total time taken for key generation is  "+(endtime-starttime));
	pr.println("Time taken for key generation of "+primeSize+" bit key is :"+ (endtime-starttime));
       
        }


	/**
	 * Generate two distinct large prime numbers p and q.
	 */
	public void generatePrimeNumbers()
	{
            //System.out.println
           
		p = new BigInteger( primeSize, 10, new Random() ) ;


		do
		{
			q = new BigInteger( primeSize,10, new Random() ) ;
		}
		while( q.compareTo( p ) == 0 ) ;
             
            
                
	}
        
        
        public void generatePrimeNumbers(int probability)
	{
            //System.out.println
                        
		p = new BigInteger( primeSize, probability, new Random() ) ;


		do
		{
			q = new BigInteger( primeSize,probability, new Random() ) ;
		}
		while( q.compareTo( p ) == 0 ) ;
            
            
                
	}
        
        public long getCurrentTime()
        {
                java.util.Date date=Calendar.getInstance().getTime();
          Timestamp a=new Timestamp(date.getTime()); 
          long currentTime=Calendar.getInstance().getTimeInMillis();
                System.out.println("Time: "+currentTime);
                
                return currentTime;
        }
            


	/**
	 * Generate Public and Private Keys.
	 */
	public void generatePublicPrivateKeys()
	{
		// N = p * q
		N = p.multiply( q ) ;


		// r = ( p - 1 ) * ( q - 1 )
		r = p.subtract( BigInteger.valueOf( 1 ) ) ;
		r = r.multiply( q.subtract( BigInteger.valueOf( 1 ) ) ) ;


		// Choose E, coprime to and less than r
		do
		{
			E = new BigInteger( 2 * primeSize, new Random() ) ;
		}
		while( ( E.compareTo( r ) != -1 ) || ( E.gcd( r ).compareTo( BigInteger.valueOf( 1 ) ) != 0 ) ) ;


		// Compute D, the inverse of E mod r
		D = E.modInverse( r ) ;
	}


	/**
	 * Encrypts the plaintext (Using Public Key).
	 *
	 * @param	message			String containing the plaintext message to be encrypted.
	 * @return	The ciphertext as a BigInteger array.
	 */
	public BigInteger[] encrypt( String message ,int blocksize)
	{
            long startencrypt=getCurrentTime();
		int i ;
		byte[] temp = new byte[blocksize] ;


		byte[] digits = message.getBytes() ; 
                int digitLength = digits.length;
                int add = digits.length%blocksize==0?0:1;

		BigInteger[] bigdigits = new BigInteger[digits.length/blocksize+add] ;
int x=0;
		for( i = 0 ; i < digitLength ; i+=blocksize )
		{
		for( int j=0; j < blocksize && (i+j)< digitLength; j++ ){	
                    temp[j] = digits[i+j] ;}
			bigdigits[x] = new BigInteger( temp ) ;
		x++;
                }

		BigInteger[] encrypted = new BigInteger[bigdigits.length] ;

		for( i = 0 ; i < bigdigits.length ; i++ )
			encrypted[i] = bigdigits[i].modPow( E, N ) ;
long endencrypt=getCurrentTime();
System.out.println("Total time taken for encryption is  "+(endencrypt-startencrypt));
pr.println("Time taken for key encryption when key size is  "+primeSize+" is :"+ (endencrypt-startencrypt));
		return( encrypted ) ;
	}


	/**
	 * Decrypts the ciphertext (Using Private Key).
	 *
	 * @param	encrypted		BigInteger array containing the ciphertext to be decrypted.
	 * @return	The decrypted plaintext.
	 */
	public String decrypt( BigInteger[] encrypted )
	{     
             long startdecrypt=getCurrentTime();
		int i ;


		BigInteger[] decrypted = new BigInteger[encrypted.length] ;

		for( i = 0 ; i < decrypted.length ; i++ )
			decrypted[i] = encrypted[i].modPow( D, N ) ;

		//char[] charArray = new char[decrypted.length] ;
                String decryptText = "";
                for (i=0; i<decrypted.length; i++)
                {
                    byte [] temp = decrypted[i].toByteArray();
                    decryptText += new String(temp);
                }

		/*for( i = 0 ; i < charArray.length ; i++ )
			charArray[i] = (char) ( decrypted[i].intValue() ) ;
 long enddecrypt=getCurrentTime();
 System.out.println("Total time taken for decryption is  "+(enddecrypt-startdecrypt));

		return( new String( charArray ) ) ;*/
 long enddecrypt=getCurrentTime();
 System.out.println("Total time taken for decryption is  "+(enddecrypt-startdecrypt));
 pr.println("Time taken for key decryption when key size is  "+primeSize+" is :"+ (enddecrypt-startdecrypt));
                return (decryptText);
	}


	/**
	 * Get prime number p.
	 *
	 * @return	Prime number p.
	 */
	public BigInteger getp()
	{
		return( p ) ;
	}


	/**
	 * Get prime number q.
	 *
	 * @return	Prime number q.
	 */
	public BigInteger getq()
	{
		return( q ) ;
	}


	/**
	 * Get r.
	 *
	 * @return	r.
	 */
	public BigInteger getr()
	{
		return( r ) ;
	}


	/**
	 * Get modulus N.
	 *
	 * @return	Modulus N.
	 */
	public BigInteger getN()
	{
		return( N ) ;
	}


	/**
	 * Get Public exponent E.
	 *
	 * @return	Public exponent E.
	 */
	public BigInteger getE()
	{
		return( E ) ;
	}


	/**
	 * Get Private exponent D.
	 *
	 * @return	Private exponent D.
	 */
	public BigInteger getD()
	{
		return( D ) ;
	}



	/**
	 * RSA Main program for Unit Testing.
	 */
	public static void main( String[] args ) throws Exception
	{
new RSA();		
RSA.pr.println("The Statistics after execution of RSA algorithm");
RSA.pr.println("");
RSA.pr.println("---------------------------------------------------------------------------");
                int keysize[]={128,256,512,768,1024};
		// Get bit length of each prime number
                for(int k=0; k<keysize.length;k++){
        		int primeSize = keysize[k];
                        int blocksize= primeSize/8;

		// Generate Public and Private Keys
	
RSA rsa = new RSA( primeSize ) ;
RSA.pr.println("");
		System.out.println( "Key Size: [" + primeSize + "]" ) ;
		System.out.println( "" ) ;

		System.out.println( "Generated prime numbers p and q" ) ;
		System.out.println( "p: [" + rsa.getp().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "q: [" + rsa.getq().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "" ) ;

		System.out.println( "The public key is the pair (N, E) which will be published." ) ;
		System.out.println( "N: [" + rsa.getN().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "E: [" + rsa.getE().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "" ) ;

		System.out.println( "The private key is the pair (N, D) which will be kept private." ) ;
		System.out.println( "N: [" + rsa.getN().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "D: [" + rsa.getD().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "" ) ;


		// Get message (plaintext) from user
		System.out.println( "Please enter message (plaintext):" ) ;
           
		//String plaintext = ( new BufferedReader( new InputStreamReader( System.in ) ) ).readLine() ;
                String plaintext="This is the RSA algorithm";
                System.out.println( plaintext ) ;

		// Encrypt Message
		RSA.pr.println("");
                BigInteger[] ciphertext = rsa.encrypt( plaintext ,blocksize) ;

		System.out.print( "Ciphertext: [" ) ;
		for( int i = 0 ; i < ciphertext.length ; i++ )
		{
			System.out.print( ciphertext[i].toString( 16 ).toUpperCase() ) ;

			if( i != ciphertext.length - 1 )
				System.out.print( " " ) ;
		}
		System.out.println( "]" ) ;
		System.out.println( "" ) ;

RSA.pr.println("");
		String recoveredPlaintext = rsa.decrypt( ciphertext ) ;

		System.out.println( "Recovered plaintext: [" + recoveredPlaintext + "]" ) ;
	}
                RSA.pr.println(" there statistics are for the different file sizes");
                RSA.pr.println("");
                RSA.pr.println("the order is .5KB , 1KB , 1.5 KB ,2 KB , 3.5 KB");
             RSA.pr.println("");
                String filenames[]={"both.c","README","data","er","aas"};
                int keys[]={128,256};
                for(int i=0;i<filenames.length;i++){
                for(int j=0;j<keys.length;j++){
                    
                     BufferedReader in =
new BufferedReader(
new FileReader("/assign/"+filenames[i]));
String s, plaintext1 = new String();
while((s = in.readLine())!= null)
plaintext1 += s ;
in.close();

RSA rsa1 = new RSA( keys[j] ) ;

		System.out.println( "Key Size: [" + keys[j] + "]" ) ;
		System.out.println( "" ) ;

		System.out.println( "Generated prime numbers p and q" ) ;
		System.out.println( "p: [" + rsa1.getp().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "q: [" + rsa1.getq().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "" ) ;

		System.out.println( "The public key is the pair (N, E) which will be published." ) ;
		System.out.println( "N: [" + rsa1.getN().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "E: [" + rsa1.getE().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "" ) ;

		System.out.println( "The private key is the pair (N, D) which will be kept private." ) ;
		System.out.println( "N: [" + rsa1.getN().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "D: [" + rsa1.getD().toString( 16 ).toUpperCase() + "]" ) ;
		System.out.println( "" ) ;


		// Get message (plaintext) from user
		System.out.println( "Please enter message (plaintext):" ) ;
           
		//String plaintext = ( new BufferedReader( new InputStreamReader( System.in ) ) ).readLine() ;
                
                System.out.println( plaintext1 ) ;

		// Encrypt Message
		BigInteger[] ciphertext = rsa1.encrypt( plaintext1 ,keys[j]/8) ;

		System.out.print( "Ciphertext: [" ) ;
		for( int l = 0 ; l < ciphertext.length ; l++ )
		{
			System.out.print( ciphertext[l].toString( 16 ).toUpperCase() ) ;

			if( l!= ciphertext.length - 1 )
				System.out.print( " " ) ;
		}
		System.out.println( "]" ) ;
		System.out.println( "" ) ;


		String recoveredPlaintext = rsa1.decrypt( ciphertext ) ;

		System.out.println( "Recovered plaintext: [" + recoveredPlaintext + "]" ) ;
                }}
                
                   
                RSA.pr.println("");
                RSA.pr.println("----------------------------------------------------");
RSA.pr.println("");
RSA.pr.println("");
RSA.pr.println("");
      RSA.pr.println(" This section contains various statistics generated after varying probability of being an integer prime");
      int probability[]={5,15,25,50};
      for(int b=0; b<probability.length;b++){
          RSA.pr.println("");
          RSA.pr.println("the key generation time when probability is "+probability[b]+" : ");
          new RSA(512,probability[b]);
          RSA.pr.println("");
          
      }
      
        }
        
         
}