A method and apparatus for encryption of data are provided, in which the data is made up of a series of data items (600). The data items (600) maybe bytes of data or blocks of data. The method includes providing a plurality of encryption algorithms (604), selecting when to change encryption algorithm (601), selecting which encryption algorithm to change to (603), wherein each selection is carried out by applying a Chaotic and/or Catastrophic equation. The plurality of encryption algorithms (604) have index numbers and the generation of an index number by applying the Chaotic or Catastrophic equation selects an encryption algorithm. The selection of when to change encryption algorithm may be determined by a Catastrophic event in the Catastrophic equation and the selection of encryption algorithm may be determined by the surface of a Catastrophic curve on which a point lies, wherein each surface corresponds to an encryption algorithm. The selection of when to change encryption algorithm may be carried out by generating a data item count by applying a Chaotic equation and the encryption algorithm may be selected by generating its index number by applying a Chaotic equation.