The present invention is directed to systems and methods for protecting digital content during transmission. One version of the invention provides a method for encryption in a high-speed digital video transmission system that includes the steps of: a) performing transition controlled encoding of a first sequence of n bit data words into encoded n+1 bit data characters where the n is a positive integer, b) performing XOR masking of the encoded n+1 bit data characters with an XOR mask to produce masked n+1 bit data characters; c) DC balancing the masked n+1 bit data characters to produce DC balanced, masked n+2 bit data characters; d) scrambling the DC balanced, masked n+2 bit data characters using a scrambling formula to produce encrypted n+2 bit data characters; e) encoding control data into encoded n+2 bit control characters, f) generating a serial data stream in response to the encrypted data characters and encoded control characters, and g) transmitting the serial data stream over a communication link. Subsequent to step (e) and prior to step (f), the method can further include the step of encrypting the encoded n+2 bit control characters, such that the generating step generates a serial data stream in response to the encrypted data characters and the encrypted control characters.