Question

i need some idea for creatin a encryption program can any one help!?
i need to create the program in java or c++ so need to create a logic for it
this encryption prog should automatically encrypt the document n should decrypt it only if the givien conditions such as the password are fulfilled !
plz help !

Answer 1

I agree with fielding. in case you want to do your homework, I think it’s OK to use XOR encryption:

Java Sample Code:

public String xorEnc(int encKey, String toEnc) {
    /*
        Usage: str = xorEnc(integer_key,string_to_encrypt);
        Created by Matthew Shaffer (matt-shaffer.com)
    */
    int t=0;
    String s1="";
    String tog="";
    if(encKey>0) {
        while(t < toEnc.length()) {
            int a=toEnc.charAt(t);
            int c=a ^ encKey;
            char d=(char)c;
            tog=tog+d;
            t++;
        }

    }
    return tog;
}
public String xorEncStr(String encKey, String toEnc) {
    /*
        Usage: str = xorEnc(string_key,string_to_encrypt);
        Created by Matthew Shaffer (matt-shaffer.com)
    */
    int t=0;
    int encKeyI=0;

    while(t < encKey.length()) {
        encKeyI+=encKey.charAt(t);
        t+=1;
    }
    return xorEnc(encKeyI,toEnc);
}

you may want to start the decryption process only if the correct password entered, then you should somehow store the hash of decryption password on the encrypted file.
for example your encrypted file may look like this:

[MD5 HASH OF PASSWORD][Encrypted Data]

then compare the entered password hash with the one you have saved, if they’re identical start decryption process.