combine two byte[] in SHA512Digest 's doFinal - byte

Question

in this methode there is only one instruction that not working:
private static byte[] encodePassword(String password,String salt) throws UnsupportedEncodingException
{
String mergedPasswordAndSalt =mergePasswordAndSalt(password, salt);
SHA512Digest digester =new SHA512Digest();
byte[] hash = new byte[digester.getDigestSize()];
digester.update(hash, 0, mergedPasswordAndSalt.length());
digester.doFinal(hash, 0);
System.out.println("init hash= "+Base64.encode(hash));
for (int i = 1; i < ITERATIONS; ++i) {
digester.update(hash, 0, mergedPasswordAndSalt.length());
digester.doFinal(Bytes.concat(hash, mergedPasswordAndSalt.getBytes("UTF-8")),0);
}
System.out.println("FINAL hash= "+Base64.encode(hash));
return hash;
}
that instructions: is the equivalent of this one in the java api that is way:
for (int i = 1; i < ITERATIONS; ++i) {
hash = digester.digest(Bytes.concat(hash, mergedPasswordAndSalt.getBytes("UTF-8")));
}

Answer 1

I have the solution:
To concat bytes i used this method:
public static byte[] concat(byte[]... arrays) {
int length = 0;
byte[][] arr$ = arrays;
int pos = arrays.length;
for(int i$ = 0; i$ < pos; ++i$) {
byte[] array = arr$[i$];
length += array.length;
}
byte[] result = new byte[length];
pos = 0;
byte[][] arr$$=arrays;
arr$=arr$$;
int len$ = arrays.length;
for(int i$ = 0; i$ < len$; ++i$) {
byte[] array = arr$[i$];
System.arraycopy(array, 0, result, pos, array.length);
pos += array.length;
}
return result;
}
To do 4999 iteration on the digest we need a method that takes the hash after every iteration and works in the current digest concatenated with the first diegest(generate out of loop):
private static byte[] encodePassword(String password,String salt) throws UnsupportedEncodingException
{
String mergedPasswordAndSalt =mergePasswordAndSalt(password, salt);
byte[] hash = new byte[88];
hash=digestt(mergedPasswordAndSalt.getBytes("UTF-8"));
for (int i = 1; i < ITERATIONS; ++i) {
hash=digestt(concat(hash,mergedPasswordAndSalt.getBytes("UTF-8")));
}
return hash;
}
public static byte[] digestt(byte[] bytes) {
Digest digest = new SHA512Digest();
byte[] resBuf = new byte[digest.getDigestSize()];
digest.update(bytes, 0, bytes.length);
digest.doFinal(resBuf, 0);
return resBuf;
}
thank you very much i asked many questions and you are always there for help.