public Key(byte[] hash){
  if (hash.length != SHA1_HASH_LENGTH) {
    throw new IllegalArgumentException("Invalid Hash must be 20bytes, was: " + hash.length);
  }
  System.arraycopy(hash,0,this.hash,0,SHA1_HASH_LENGTH);
}

public Key ( byte [ ] hash ) { if ( hash . length != SHA1_HASH_LENGTH ) { throw new IllegalArgumentException ( "Invalid Hash must be 20bytes, was: " + hash . length ) ; } System . arraycopy ( hash , 0 , this . hash , 0 , SHA1_HASH_LENGTH ) ; }
creates a key with this hash
