A method for generating, from initial content data, output content data for provision to one or more receivers, wherein the initial content data is encoded according to a coding scheme, wherein the coding scheme provides a mechanism that uses a predetermined first code and one or more predetermined second codes such that a decoder for the coding scheme ignores data located between a first code and a corresponding following second code when generating decoded data, the method comprising: selecting one or more portions of the initial content data; for each selected portion, generating a data construct that comprises a plurality of data structures, each data structure comprising data, including a version of the selected portion, that is encrypted using a corresponding encryption process different from each encryption process used to encrypt data in the other data structures, wherein the data construct is arranged such that using a decryption process that corresponds to the encryption process for one data structure on the encrypted data in each data structure in the data construct produces a quantity of data encoded according to the coding scheme that uses the mechanism so that a decoder for the coding scheme would ignore any data structure in the data construct other than said one data structure when generating decoded data; and using the generated data constructs in the initial content data instead of their corresponding selected portions to form the output content data; wherein, for a given data structure in a data construct: (a) the corresponding data that is encrypted using the corresponding encryption process commences with one of the one or more predetermined second codes so that, upon performance of the corresponding decryption process for said given data structure on the encrypted data in each data structure in that data construct, any data structure in that data construct preceding said given data structure occurs between a first code in the data construct and the decrypted second code in said given data structure; and/or (b) the corresponding data that is encrypted using the corresponding encryption process terminates with a first code, so that, upon performance of the corresponding decryption process for said given data structure on the encrypted data in each data structure in that data construct, any data structure in the data construct following said given data structure occurs between the decrypted first code in said given data structure and a corresponding subsequent second code. selecting one or more portions of the initial content data; for each selected portion, generating a data construct that comprises a plurality of data structures, each data structure comprising data, including a version of the selected portion, that is encrypted using a corresponding encryption process different from each encryption process used to encrypt data in the other data structures, wherein the data construct is arranged such that using a decryption process that corresponds to the encryption process for one data structure on the encrypted data in each data structure in the data construct produces a quantity of data encoded according to the coding scheme that uses the mechanism so that a decoder for the coding scheme would ignore any data structure in the data construct other than said one data structure when generating decoded data; and using the generated data constructs in the initial content data instead of their corresponding selected portions to form the output content data; wherein, for a given data structure in a data construct: (a) the corresponding data that is encrypted using the corresponding encryption process commences with one of the one or more predetermined second codes so that, upon performance of the corresponding decryption process for said given data structure on the encrypted data in each data structure in that data construct, any data structure in that data construct preceding said given data structure occurs between a first code in the data construct and the decrypted second code in said given data structure; and/or (b) the corresponding data that is encrypted using the corresponding encryption process terminates with a first code, so that, upon performance of the corresponding decryption process for said given data structure on the encrypted data in each data structure in that data construct, any data structure in the data construct following said given data structure occurs between the decrypted first code in said given data structure and a corresponding subsequent second code. (a) the corresponding data that is encrypted using the corresponding encryption process commences with one of the one or more predetermined second codes so that, upon performance of the corresponding decryption process for said given data structure on the encrypted data in each data structure in that data construct, any data structure in that data construct preceding said given data structure occurs between a first code in the data construct and the decrypted second code in said given data structure; and/or (b) the corresponding data that is encrypted using the corresponding encryption process terminates with a first code, so that, upon performance of the corresponding decryption process for said given data structure on the encrypted data in each data structure in that data construct, any data structure in the data construct following said given data structure occurs between the decrypted first code in said given data structure and a corresponding subsequent second code.