CODEWITHSUNDEEP
javamessage-digest
discodane
discodane

Reputation: 2095

Java messageDigest funky output

I'm using Java's MessageDigest to do a hashing project. I want to create collisions with hashes made by randomly generated strings. I have verified that my strings are truly random. When I output the digest however it always begins with "[B@" for some reason and when I'm trying to detect a collision with 8 bits obviously everything starts with "[". Here is my code:

public boolean encrypt(String x) throws Exception {
    System.out.println("x is " + x);
    java.security.MessageDigest d = java.security.MessageDigest.getInstance("SHA-1");
    d.update(x.getBytes());
    d.reset();
    String result = d.digest().toString() + "     ";
    char[] tempCharArray = result.toCharArray();
    String bitArray = "";
    for(int i=0; i< tempCharArray.length; i++){
        bitArray += String.format("%8s", Integer.toBinaryString(tempCharArray[i] &
          0xff)).replace(' ', '0');
    }

    result = bitArray.substring(0,8);
    return result;
}

Has anyone seen this before/ know what to do to get it right? Thanks

Upvotes: 0

Views: 687

Answers (1)

Qwerky
Qwerky

Reputation: 18445

You look to be doing some strange stuff in your code.

First, you call;

String result = d.digest().toString()

..which is going to give you the string representation of a byte array object, which is made of the class name, an "@" symbol, and the hashcode. Arrays have a class name of "[B", hence you will always get something starting "[B@".

Secondly you call d.update(x.getBytes()) and then immediately call d.reset(). Even if you fix the first problem you are digesting nothing, irrespective of the value of x, so you will always get the same result, the SHA-1 hash of an empty string, which is da39a3ee5e6b4b0d3255bfef95601890afd80709.

Upvotes: 2

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