SIM lock

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A SIM lock, confused with PIN or PUK code, is a capability built-in to GSM phones by mobile phone manufacturers. Network providers use this capability to restrict the use of in these phones to specific countries and network providers. Currently, phones can be locked to only accept SIM cards from one or more of the following:

  • Countries (your phone will work in the US, but not the UK)
  • Network providers (e.g. T-Mobile, Orange, etc)
  • Service providers (another name for network providers)
  • SIM types (i.e. only specific SIM cards can be used with the phone).

Virtually all mobile phones are shipped with country and network provider locks. In addition, most modern phones have firmware installed on them which is specific to the network provider. If you have a Cingular phone, it displays the Cingular logo and supports only Cingular features. This firmware is installed by the service provider and is separate from the locking mechanism. You can unlock a Cingular phone to work with a T-Mobile network, but the phone will still display the Cingular logo and only support Cingular features. Phones can be unbranded by uploading a different firmware version, a procedure recommended for advanced users only.

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[edit] Types of SIM locks

The country lock only allows the use of the phone with SIM cards that originated in a specific country or group of countries.

A network lock only allows the use of the phone with SIM cards that belong to a specific network.

The most common lock is the service provider lock (SP-lock). Many different service providers may use the same physical network (e.g. MVNOs). An SP-lock ensures that the handset is only used with SIM cards for the same service provider that marketed the handset. Service providers sometimes substantially subsidize handsets, and locking the handset improves the odds that its use will economically benefit the service provider.

With this type of lock it's often possible to buy a cheap pay-as-you-go handset, and replace the SIM card with your current subscription SIM card from the same service provider. In this way you can buy a cheap subsidized handset, while retaining your existing subscription. However, some service providers use a different service provider code for their pay-as-you-go handsets, so it won't recognize a subscription SIM card as being from the same service provider.

The most restrictive type of lock which can be used is the full SIM card lock, which means that a phone will only work with one SIM card. If that SIM card malfunctions or is damaged, the phone will no longer work and must be serviced.

[edit] Laws on SIM locking

At this time in most countries it is either mandatory or voluntary for the provider to unlock the customer's mobile phone. However, some providers, including the former AT&T Wireless, never unlock handsets, even after a customer has fulfilled their service contract.[citation needed] Other providers, for example T-Mobile and more recently Cingular will unlock phones if the customer has an active account in good standing for at least 90 days.[1]

UK network providers are permitted to charge a fee for releasing the unlock code. This has prompted smaller businesses to offer cut price unlocking on the UK’s High Streets, marketplaces and car boot sales.

Belgium doesn't allow networks to sell locked handsets. In The Netherlands, providers must provide unlocking codes, but can charge a fee for this during the first 12 months after purchase; the unlocking code must be provided at no cost after this period of time.[citation needed]

In Hong Kong, networks are not allowed to sell locked mobile phones, with the exception of some PDA phone models, such as those offered by BlackBerry.

[edit] Unlocking Technology

A handset can be unlocked by entering a special code, or in some cases, over-the-air by the carrier.

Typically, a locked phone will display a message if a restricted SIM is used, requesting the unlock code.

For example, on the Sony Ericsson T610 mobile phone, "Insert correct SIM card" will appear on the phone's display if the wrong SIM is used. Once a valid unlocking code is entered, the phone will display "Network unlocked". In some cases, the phone will simply display a message explaining that it is locked. This is especially the case with handsets provided by Cingular Wireless.

The code required to remove all SIM locks from a phone is called the master code or network code key.

The unlock code is verified by the phone itself, and is either stored in a database or calculated using an obscure mathematical formula by the provider.

The algorithms used in earlier Nokia brand phones (based on IMEI and MCC code) have been reverse engineered, stolen or leaked, resulting in many people offering nokia unlock codes for free or for a fee. Newer Nokia phones have more robust encoding algorithms and permit fewer attempts at unlocking and are not unlockable by the free unlocking programs out there.

Many other manufacturers have taken a more cautious approach, and embed a random number in the handset's firmware that is only retained by the network on whose behalf the lock was applied. Such phones can often still be unlocked, but need to be connected to special test equipment that will rewrite that part of its firmware where the lock status is kept.

Most phones have security measures built in its software that prevent users from entering the unlock code too many times, usually four. After that the phone becomes "hard-locked" and special unlocking equipment has to be used in order to unlock it.

Handset manufacturers have economic incentives both to strengthen simlock security (which placates network providers and enables exclusivity deals), but also to weaken it (broadening a handset's appeal to customers who are not interested in the service provider that offers it). Also, making it too difficult to unlock a handset makes it less appealing to network service providers that have a legal obligation to provide unlock codes for every handset they've ever sold.

The main reason to unlock a phone is to be able to use it with a different SIM card. For example, when travelling abroad it's usually cheaper to temporarily use a foreign network. Contrary to some beliefs, an unlocked phone can't access extra cell phone towers or give free phone service. All it can do is accept other SIMs.

In some cases, a simlocked handset is sold at a substantially lower price than an unlocked one, because the service provider expects income through its service. A consumer may choose to unlock the phone and continue using his previous provider. Therefore, simlocks are usually employed on cheaper (pay-as-you-go) handsets, while discounts on more expensive handsets require a subscription that provides guaranteed cash flow.

A practice known as "box breaking" is common in the UK and some other markets. This involves purchasing (usually) pay as you go handsets from retail stores, unlocking the phones, and then selling them (often abroad) for a higher price than the subsidised retail price. The SIM card that came with the subsidised handset is then either thrown away or sold or used elsewhere. This practice is entirely legal in the UK, and provides a de-facto limit to the extent to which networks are willing to subsidise pay as you go handsets. In recent times network operators have been insisting that new customers purchase substantial amounts of airtime at the same time as they buy a new handset, in order that the total price they pay comes close to the true value of the handset.

[edit] Unlocking via computer

One of the most popular ways phones are unlocked is using the RS-232 or LPT port of a computer using software usually written specifically for the model of phone being unlocked. In some cases, special "unlocking clips" or "unlocking boxes" are used which re-program the software that controls the phone, removing the SIM lock. However, such clips are usually very expensive.

[edit] Regulations on unlocking

Unlocking a phone without the permission or unlocking code from the provider is usually in breach of the agreement with the provider, though most countries do not make specific laws prohibiting the removal of SIM locks. (In many markets, it is also unlikely that a customer who has purchased a pay as you go phone over the counter in a store is legally bound by any such contract anyway). For example, in Poland, the law states that providers cannot word their customer contracts so that they forbid the removal of SIM locks, and the process is entirely legal providing that the IMEI number of the phone is not changed during the unlocking process.

In the United Kingdom under the Mobile Telephones (Re-programming) Act 2002, changing the IMEI of the phone is illegal. However, the IMEI is not changed during any unlocking process.

In the Netherlands unlocking is legal provided that the process does not overwrite the handset's flash memory with a (modified) copy of copyrighted firmware, since this would be a breach of copyright retained by the manufacturer. However, unlocking a handset will void its warranty.

In the United States under new copyright rules, cellular phone unlocking is now legal. The new rules took effect November 27, 2006 and will expire in three years.

[edit] See also

[edit] External links

  • Free Phone Unlocking - Free Information, secret codes, resources, and software relating to mobile phone unlocking (US based).
  • E-Ireland - Free Online Nokia Unlock Calculator
  • Mr Unlock - Paid service with support and contact details.
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