A SIM (subscriber identity module) card is an application on a smartcard that stores data for GSM/CDMA Cellular telephone subscribers.
The SIM contains a cryptographic chip, but critically it also stores a copy of the unique subscriber key, the other copy being held in the network operator's authentication server. During the GSM authentication a random number is encrypted by the server using that key and must be decrypted by the phone to prove the subscriber is genuine. The chips, holding the key and doing the cryptography are glued to the back of the SIM's metal contacts.
Additional data stored on a SIM are contact lists, stored text messages etc.
Evolution of SIM
When the GSM network first appeared SIM cards were the size of credit cards. The subsequent miniaturization of the phones led to the standardization of smaller SIMs, the Plug-in SIM, and later the Mini-UICC, also known as 3rd form factor (3FF) or Micro-SIM.
Nano-SIM
The latest form factor is the 4th form factor or Nano-SIM, introduced in early 2012. Measuring 12.3 x 8.8 x 0.67 mm the Nano-SIM is about 30 percent smaller than the Micro-SIM. The Nano-SIM offers device manufacturers the crucial advantage of freeing up extra space for other mobile phone components such as additional memory or larger batteries and also, to produce devices that are thinner and more appealing.
Nano SIM Structure
There are eight connections on all the SIM designs, although on both the traditional SIM and the Micro-SIM (3FF) the electrical ground connection (C5, see diagram) is generally extended down the middle. That's harder on the nano SIM because it has two connections in the middle (C4 and C8).
Contacts on the nano SIM.
Of the eight contacts, three are optional, but in most cases six pads will be visible. C1 is the supply voltage; C2 is the reset signal so the SIM knows when to start doing something; and C3 is the clock signal as the timing clock was left out of the SIM spec to keep the cost down. C5 is ground; C6 is the NFC SWP contact; and C7 is the serial communications connection that actually does the task execution one expects a SIM to do.
Apple's iPhone 5 uses nano SIM.
References:
http://en.wikipedia.org/wiki/Subscriber_identity_module
http://www.theregister.co.uk/2012/09/18/nano_sim/
http://www.gi-de.com/gd_media/media/en/documents/brochures/mobile_security_2/cste_1/Nano-SIM.pdf
The SIM contains a cryptographic chip, but critically it also stores a copy of the unique subscriber key, the other copy being held in the network operator's authentication server. During the GSM authentication a random number is encrypted by the server using that key and must be decrypted by the phone to prove the subscriber is genuine. The chips, holding the key and doing the cryptography are glued to the back of the SIM's metal contacts.
Additional data stored on a SIM are contact lists, stored text messages etc.
Evolution of SIM
When the GSM network first appeared SIM cards were the size of credit cards. The subsequent miniaturization of the phones led to the standardization of smaller SIMs, the Plug-in SIM, and later the Mini-UICC, also known as 3rd form factor (3FF) or Micro-SIM.
Nano-SIM
The latest form factor is the 4th form factor or Nano-SIM, introduced in early 2012. Measuring 12.3 x 8.8 x 0.67 mm the Nano-SIM is about 30 percent smaller than the Micro-SIM. The Nano-SIM offers device manufacturers the crucial advantage of freeing up extra space for other mobile phone components such as additional memory or larger batteries and also, to produce devices that are thinner and more appealing.
Nano SIM Structure
There are eight connections on all the SIM designs, although on both the traditional SIM and the Micro-SIM (3FF) the electrical ground connection (C5, see diagram) is generally extended down the middle. That's harder on the nano SIM because it has two connections in the middle (C4 and C8).
Contacts on the nano SIM.
Of the eight contacts, three are optional, but in most cases six pads will be visible. C1 is the supply voltage; C2 is the reset signal so the SIM knows when to start doing something; and C3 is the clock signal as the timing clock was left out of the SIM spec to keep the cost down. C5 is ground; C6 is the NFC SWP contact; and C7 is the serial communications connection that actually does the task execution one expects a SIM to do.
Apple's iPhone 5 uses nano SIM.
References:
http://en.wikipedia.org/wiki/Subscriber_identity_module
http://www.theregister.co.uk/2012/09/18/nano_sim/
http://www.gi-de.com/gd_media/media/en/documents/brochures/mobile_security_2/cste_1/Nano-SIM.pdf
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