question: public static CipherParameters makePBEMacParameters ( PBEKeySpec keySpec , int type , int hash , int keySize ) { PBEParametersGenerator generator = makePBEGenerator ( type , hash ) ; byte [ ] key ; CipherParameters param ; key = convertPassword ( type , keySpec ) ; generator . init ( key , keySpec . getSalt ( ) , keySpec . getIterationCount ( ) ) ; param = generator . generateDerivedMacParameters ( keySize ) ; for ( int i = 0 ; i != key . length ; i ++ ) { key [ i ] = 0 ; } return param ; }
target:  generate a PBE based key suitable for a MAC algorithm, the key size is chosen according the MAC size, or the hashing algorithm, whichever is greater.