Television scrambler
AssigneeDCE Voice Processing Limited
InventorsDavid J. Millar, Stephen J. Greenhalgh, Richard P. Gregory
Life of this patent
Estimating the term…
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.
Claims15
Apparatus for encrypting or decrypting a signal comprising a series of values or groups of values, comprising
- a memory having a predetermined number of storage locations or groups of locations;
- means for reading output values or groups of output values from, and writing new input values or groups of input values into, each of said locations or groups of locations in a first predetermined order until the said predetermined number is reached, and further for reading output values or groups of output values from, and writing new input values or groups of values into, each of said locations or groups of locations in a second predetermined order until the said predetermined number is reached;
- and control means for causing the reading and writing operations to be repeated alternately in the two said predetermined orders.
A method of encrypting or decrypting a signal comprising a series of values or groups of values, using a predetermined number of storage locations or groups of locations in a block of memory, the method comprising the steps of:
- (a) reading output values or groups of output values from, and writing new input values or groups of input values into, each of said locations or groups of locations in a first predetermined order until the said predetermined number is reached;
- (b) reading output values or groups of output values from, and writing new input values or groups of values into, each of said locations or groups of locations in a second predetermined order until the said predetermined number is reached;
- and
- (c) subsequently repeating steps (a) and (b) alternately.
Dependencies are inferred from the claim text.