Reprogramming the identification number of a cellphone could be punishable with a prison sentence of up to five years under the terms of a proposed federal law introduced Friday. The Mobile Device Theft Deterrence Act of 2013 makes changing the International Mobile Equipment Identity (IMEI) number in a phone a crime. The IMEI number is a unique identification number in every cellphone and is exchanged when a mobile phone signs on to a mobile network. In an attempt to combat the growing number of violent street robberies of high-end smartphones, carriers have built a database that blocks stolen phones from being reused. The database relies on the IMEI number, so if the number is reprogrammed in a stolen handset, it could bypass the database check and get resold and reused. Reprogramming the number isn't easy, but it also represents a weak point in the battle against these robberies, which now account for close to half of all street crime in several major U.S. cities. While the theft of the phone and the sale of stolen goods both constitute crimes, the electronic reprogramming in the middle doesn't. The new law would change that.