A method and system for processing a data set. More particularly, the present invention provides a method and system for encrypting or decrypting a data set so that the data set remains entirely in the ASCII printable range. The method and system of the present invention allow a key of any length to be selected. Once selected, the key is formatted to the length of the data set and then masked so that predetermined bits are set to zero. An exclusively-OR result is then formed with the data set and the masked key to yield an encrypted data set.