1. A method for storing a vector of process data elements that have a size of n bits from a register file into a memory, the memory arranged for storage of a vector of storage data elements in locations having a size of m bits, wherein m>n, the method comprising: exchanging bits between process data elements in the vector stored in mutually subsequent register elements, the exchange producing a vector of modified data elements, whereby the size of at least one modified data element is different from the size of another modified data element; shuffling groups of k subsequent bits in the produced vector whereby for at least one group of k subsequent bits, k has a value which is different from n and m; and storing the shuffled vector of modified data elements as a vector of storage data elements in the memory.