While a 2-byte seed only has 65,535 possible combinations (which a computer can guess in days), a 5-byte seed has over 1 trillion combinations , making "guessing" virtually impossible.
// Simplified conceptual logic // Input: 5-byte Seed // Output: 5-byte Key gm 5 byte seed key
Both the ECU and the tool run this Seed through a proprietary, secret mathematical function (the algorithm) using a specific access key or "mask" stored in the firmware. The Key Response: The tool sends its calculated 5-byte "Key" back to the ECU. Validation: While a 2-byte seed only has 65,535 possible
If you provide the wrong key too many times, the ECU will "lock out" for 10 minutes. You must leave the ignition on and wait for the timer to reset. gm 5 byte seed key