Validating download success

A computer storage device storing a computer program, the program comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising:

• receiving a request to transmit a digital item to a computing device;
• creating a modified digital item from the digital item, wherein the modified digital item includes N existing data portions replaced with N invalid data portions, wherein N is an integer greater than or equal to one;
• transmitting the modified digital item to the computing device;
• receiving confirmation that the computing device has received the modified digital item in its entirety;
• for each of the N invalid data portions included in the modified digital item:
• transmitting to the computing device:
• a location of the invalid data portion in the modified digital item and
• the existing data portion previously replaced by the invalid data portion and receiving confirmation that the computing device has received the existing data portion;
• and
• in response to receiving confirmations for each of the N existing data portions transmitted to the computing device, transmitting to the computing device an indication that the computing device has received all N existing data portions replaced by the N invalid data portions.

A system comprising:

• one or more computers;
• and
• a computer-readable medium coupled to the one or more computers having instructions stored thereon which, when executed by the one or more computers, cause the one or more computers to perform operations comprising:
• receiving a request to transmit a digital item to a computing device;
• creating a modified digital item from the digital item, wherein the modified digital item includes N existing data portions replaced with N invalid data portions, wherein N is an integer greater than or equal to one;
• transmitting the modified digital item to the computing device;
• receiving confirmation that the computing device has received the modified digital item in its entirety;
• for each of the N invalid data portions included in the modified digital item:
• transmitting to the computing device:
• a location of the invalid data portion in the modified digital item, and
• the existing data portion previously replaced by the invalid data portion, and
• receiving confirmation that the computing device has received the existing data portion;
• and
• in response to receiving confirmations for each of the N existing data portions transmitted to the computing device, transmitting to the computing device an indication that the computing device has received all N existing data portions replaced by the N invalid data portions.