1. A method of processing digital content, the method comprising: receiving, by at least one processor, content scrambled using a control word; receiving, via a user interface, a user code, wherein a user identifier and the control word are concatenated and encrypted in the user code based on a secret key; decrypting, by the at least one processor, the control word and the user identifier from the user code using the secret key; descrambling, by the at least one processor, the scrambled content using the control word; generating, by the at least one processor, a watermark based on the user identifier such that the watermark is uniquely associated with the user identifier; inserting, by the at least one processor, the watermark into the descrambled content; and outputting, by the at least one processor, the watermarked content, wherein the decrypting comprises: obtaining, by the at least one processor, an intermediate code from the user code; and decrypting, by the at least one processor, the control word and the user identifier from the intermediate code.