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The PUK, an acronym for Personal Unblocking Key, is a numeric code used to unlock a blocked SIM (Subscriber Identity Module) card. This block generally occurs after a certain number of incorrect attempts to enter the PIN (Personal Identification Number). The PUK usually consists of 8 digits and is provided by the telecommunications operator when the SIM card is purchased. The main function of the PUK is to ensure an additional security measure to protect the data and access to the mobile network.

In everyday life, the PUK comes into play when a user locks their SIM card by entering the wrong PIN multiple times in a row. Typically, if a user forgets the PIN and enters it incorrectly three times, the SIM card is blocked for security reasons. At this point, the user must enter the PUK to unlock it. If the PUK is entered correctly, the user can then create a new PIN and regain access to their SIM card and the services associated with it. If the PUK is entered incorrectly too many times, the SIM card can become unusable, requiring a replacement from the mobile provider.

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