Abstract: A video encryption/decryption system in which lines of video information are stored in digitised form in a block of RAM memory, and are typically shuffled in groups of 32 lines by pivot reading information corresponding to 32 lines from the memory in a first predetermined order, which may for example be sequential order, and writing new input line information into the corresponding locations, and then reading from, and writing to, the memory in a second different order which may be random or pseudo-random, and subsequently repeating these two read/write operations alternately. This enables the line shuffling process to be achieved with a reduced memory requirement, compared with known methods.