idea.java

IDEA is a symetric method to crypt message or document.

package idea;

public class idea{
    
    private int[][]Z=new int[6][9];
    private int[][]K=new int[6][9];
    
    public idea(String cle){ 
        byte[]cle2=new byte[16];
        for(int i=0;i<16;i++)cle2[i]=Byte.parseByte(cle.substring((i<<1),((i+1)<<1)), 16);
        Z=setKeyZ(cle2);
        K=setKeyK(Z);
    }
    
    public idea(byte[]cle){
        super();
        Z=setKeyZ(cle);
        K=setKeyK(Z);
    }
   
    public byte[] chiffre(byte[]plaintext){
        Math.random();//nombre >=0 et <1
        
        int x1,x2,x3,x4,kk,t1,t2,a;
        x1=(plaintext[0] & 0xFF) | ((plaintext[1] & 0xFF)  <<8);
        x2=(plaintext[2] & 0xFF) | ((plaintext[3] & 0xFF)  <<8);
        x3=(plaintext[4] & 0xFF) | ((plaintext[5] & 0xFF)  <<8);
        x4=(plaintext[6] & 0xFF) | ((plaintext[7] & 0xFF)  <<8);
        for(int r=0;r<8;r++){
            
            x1=mul(x1,Z[0][r]);
            x4=mul(x4,Z[3][r]);
            x2=(x2 + Z[1][r]) & 65535;
            x3=(x3 + Z[2][r]) & 65535;
            kk=mul(Z[4][r],(x1^x3));
            t1=mul(Z[5][r],(kk+(x2^x4)) & 65535);
            t2=(kk + t1) & 65535;
            x1=x1^t1;
            x4=x4^t2;
            a=x2^t2;
            x2=x3^t1;
            x3=a;
           
        }
        
        x1=mul(x1,Z[0][8]);
        x4=mul(x4,Z[3][8]);
        a=x2;
        x2=(x3 + Z[1][8]) & 65535;
        x3=(a + Z[2][8]) & 65535;
        
        byte[]ciphertext=new byte[8];
        ciphertext[0]=(byte)(x1 & 255);
        ciphertext[1]=(byte)(x1 >>> 8);
        ciphertext[2]=(byte)(x2 & 255);
        ciphertext[3]=(byte)(x2 >>> 8);
        ciphertext[4]=(byte)(x3 & 255);
        ciphertext[5]=(byte)(x3 >>> 8);
        ciphertext[6]=(byte)(x4 & 255);
        ciphertext[7]=(byte)(x4 >>> 8);
     
        return ciphertext ; 
    }


    public byte[] dechiffre(byte[] ciphertext){

        int x1,x2,x3,x4,kk,t1,t2,a;
        x1=((ciphertext[0] & 0xFF) | ((ciphertext[1] & 0xFF)  <<8));
        x2=((ciphertext[2] & 0xFF) | ((ciphertext[3] & 0xFF)  <<8));
        x3=((ciphertext[4] & 0xFF) | ((ciphertext[5] & 0xFF)  <<8));
        x4=((ciphertext[6] & 0xFF) | ((ciphertext[7] & 0xFF)  <<8));
        
        for(int r=0;r<8;r++){
            
            x1=mul(x1,K[0][r]);
            x4=mul(x4,K[3][r]);
            x2=((x2 + K[1][r]) & 65535);
            x3=((x3 + K[2][r]) & 65535);
            kk=mul(K[4][r],(x1^x3));
            t1=mul(K[5][r],(kk+(x2^x4)) & 65535);
            t2=((kk + t1) & 65535);
            x1=(x1^t1);
            x4=(x4^t2);
            a=(x2^t2);
            x2=(x3^t1);
            x3=a;
            
        }
        
        x1=mul(x1,K[0][8]);
        x4=mul(x4,K[3][8]);
        a=x2;
        x2=((x3 + K[1][8]) & 65535);
        x3=((a + K[2][8]) & 65535);
        byte[]plaintext=new byte[8];
        plaintext[0]=(byte)(x1 & 0x000000FF);
        plaintext[1]=(byte)(x1 >>> 8);
        plaintext[2]=(byte)(x2 & 0x000000FF);
        plaintext[3]=(byte)(x2 >>> 8);
        plaintext[4]=(byte)(x3 & 0x000000FF);
        plaintext[5]=(byte)(x3 >>> 8);
        plaintext[6]=(byte)(x4 & 0x000000FF);
        plaintext[7]=(byte)(x4 >>> 8);
        
        return plaintext ;  
    }
    
    public int[][] setKeyZ(byte[]cle){
        int S[]=new int[54];
        int[][]Z=new int[6][9];
        for(int i=0;i<8;i++)S[i]=(cle[2*i] & 0xFF) | ((cle[2*i+1] & 0xFF) <<8) ;
        for(int i=8;i<54;i++){
            if ((i & 7) < 6)S[i]=((S[i-7]<<9)^(S[i-6]>>>7)) & 65535;
            else if((i & 7) == 6)S[i]=((S[i-7]<<9)^(S[i-14]>>>7)) & 65535;
            else S[i]=((S[i-15]<<9)^(S[i-14]>>>7)) & 65535;
        }
        for(int i=0;i<9;i++){
            for(int j=0;j<6;j++)Z[j][i]=S[6*i+j];
        }
        return Z;
    }
    
    public int[][] setKeyK(int[][]Z){
        int[][]K=new int[6][9]; 
        for(int j=0;j<9;j++){
            K[0][8-j]=inv(Z[0][j]);
            K[3][8-j]=inv(Z[3][j]);
            if(j==0 || j==8){
                K[1][8-j]=(65536 - Z[1][j]) & 65535;
                K[2][8-j]=(65536 - Z[2][j]) & 65535;
            }else{
                K[1][8-j]=(65536 - Z[2][j]) & 65535;
                K[2][8-j]=(65536 - Z[1][j]) & 65535;
            }
        }
        for(int j=0;j<8;j++){
            K[4][j]=Z[4][7-j];
            K[5][j]=Z[5][7-j];
        }
        return K;
    }

    public int mul(int a, int b)
    {
	int p;
        int q;
	if (a == 0)
	    p = 65537- b;
        else if (b == 0)
	    p = 65537- a;
	else {
            q= a * b;
            p= ((q & 65535) - (q>>>16));
            if(p<=0)p=p+65537;
        } 
        return (p & 65535);
    }
   
    public int inv(int x)
    {
	int n1,n2,q,r,b1,b2,t;
        if(x==0)b2=0;
        else{
            n1=65537;
            n2=x;
            b2=1;
            b1=0;
            r=1;
            while(r!=0){
                r=n1%n2;
                q=(n1-r)/n2;
                if(r==0){
                    if(b2<0)b2=65537+b2;
                }else{
                    n1=n2;
                    n2=r;
                    t=b2;
                    b2=b1-q*b2;
                    b1=t;
                }
            }
        }
	return b2;
    }
}