Disclaimer: Unlocking a phone without the owner’s consent is illegal in many jurisdictions. This article is for educational and historical purposes only.
Some calculators also generate "Master Codes," which can bypass a forgotten security code (the default is usually ) to reset the device. Nokia 150 (2023) user guide: Keys and parts - HMD nokia dct4 calculator
The DCT4 security relied on a cryptographic algorithm that converted the phone’s (International Mobile Equipment Identity) and the target lock type into a 7 or 15-digit numeric code. The "calculator" essentially reverse-engineered or brute-forced this algorithm. Disclaimer: Unlocking a phone without the owner’s consent