Java: convert byte[] to base36 String

Question

I'm a bit lost. For a project, I need to convert the output of a hash-function (SHA256) - which is a byte array - to a String using base 36.

So In the end, I want to convert the (Hex-String representation of the) Hash, which is

43A718774C572BD8A25ADBEB1BFCD5C0256AE11CECF9F9C3F925D0E52BEAF89

to base36, so the example String from above would be:

3SKVHQTXPXTEINB0AT1P0G45M4KI8U0HR8PGB96DVXSTDJKI1

For the actual conversion to base36, I found some piece of code here on StackOverflow:

public static String toBase36(byte[] bytes) {
    //can provide a (byte[], offset, length) method too
    StringBuffer sb = new StringBuffer();
    int bitsUsed = 0; //will point how many bits from the int are to be encoded
    int temp = 0;
    int tempBits = 0;
    long swap;
    int position = 0;

    while((position < bytes.length) || (bitsUsed != 0)) {
        swap = 0;
        if(tempBits > 0) {
            //there are bits left over from previous iteration
            swap = temp;
            bitsUsed = tempBits;
            tempBits = 0;
        }
        //fill some bytes
        while((position < bytes.length) && (bitsUsed < 36)) {
            swap <<= 8;
            swap |= bytes[position++];
            bitsUsed += 8;
        }
        if(bitsUsed > 36) {
            tempBits = bitsUsed - 36; //this is always 4
            temp = (int)(swap & ((1 << tempBits) - 1)); //get low bits
            swap >>= tempBits; //remove low bits
            bitsUsed = 36;
        }
        sb.append(Long.toString(swap, 36));
        bitsUsed = 0;
    }
    return sb.toString();
}

Now I'm doing this:

// this creates my hash, being a 256-bit byte array
byte[] hash = PBKDF2.deriveKey(key.getBytes(), salt.getBytes(), 2, 256);

System.out.println(hash.length); // outputs "256"
System.out.println(toBase36(hash)); // outputs total crap

the "total crap" is something like

-7-14-8-1q-5se81u0e-3-2v-24obre-73664-7-5-5cor1o9s-6h-4k6hr-5-4-rt2z0-30-8-2u-8-onz-4a2j-6-8-18-8trzza3-3-2x-6-4153to-4e3l01me-6-azz-2-k-4ckq-nav-gu-irqpxx-el-1j-6-rmf8hs-1bb5ax-3z25u-2-2r-t5-22-6-6w1v-1p

so it's not even close to what I want. I tried to find a solution now, but it seems I'm a bit lost here. How do I get the base36-encoded String representation of the Hash that I need?

Answer 1

Try using BigInteger:

String hash = "43A718774C572BD8A25ADBEB1BFCD5C0256AE11CECF9F9C3F925D0E52BEAF89";
//use a radix of 16, default would be 10 
String base36 = new BigInteger( hash, 16 ).toString( 36 ).toUpperCase();

Answer 2

This might work:

BigInteger big = new BigInteger(your_byte_array_to_hex_string, 16);

big.toString(36);