In plain English:

The most reliable "paper-like" resource isn't a PDF from a university, but the open-source documentation of the algorithms used.

– Legitimate unlock codes are generated using your phone's unique IMEI number. Sharing your IMEI with untrustworthy sites poses privacy risks.

Some popular Huawei unlock code calculators include:

In May 2018, Huawei announced it would stop providing bootloader unlock codes. This caused a panic, but note: However, after this date, Huawei tightened all security modules, including SIM locks. Many carriers stopped providing NCK codes altogether, forcing customers to use the carrier’s own app (e.g., T-Mobile Device Unlock app) instead.

: Trusted platforms like Cellunlocker.net and IMEI.info allow you to submit your 15-digit IMEI number to receive a custom 16-digit unlock code.