# Encrypting PIN pad

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An **encrypting PIN pad** is an apparatus for [encrypting](/source/Encryption) an identifier such as a PIN entered on a keypad. These are used in [automated teller machines](/source/Automated_teller_machine) to ensure that the unencrypted PIN is not stored or transmitted anywhere in the rest of the system and thus cannot be revealed accidentally or through manipulations of the system.

## Apparatus

The apparatus includes a [keypad](/source/Keypad), an encrypting circuit that is adjacent the pad, and a link coupling the pad and the encrypting circuit. The pad is for entering an identifier, and the circuit for encrypting the entered identifier.[1] The pad may be a physical [touch pad](/source/Touch_pad) such as an N-wire technology touch pad. Alternatively, the pad may be a [virtual touch screen](/source/Virtual_Touch_Screen). The encrypting circuit may be a [CPU](/source/CPU) along with a memory coupled to the CPU and programmed to encrypt. The CPU and programmed [memory](/source/Memory) may be the first CPU programmable to encrypt the entered [identifier](/source/Identifier), through which the identifier passes. The encrypting circuit may be a micro controller programmed to encrypt. In still another variation, the encrypting circuit may be an application-specific [integrated circuit](/source/Integrated_circuit) ([ASIC](/source/Application-specific_integrated_circuit)). The apparatus may include a housing that encloses the encrypting circuit and link. The housing would be resistant to access, tampering or [tapping](/source/Tapping). The housing may be at least partially of chip-on-glass technology. The encrypting circuit may be [embedded](/source/Embedded_system) in the [housing](https://en.wiktionary.org/wiki/Housing), as may the link. A [method](https://en.wiktionary.org/wiki/method) for encrypting an identifier includes placing a pad for entering an identifier, a circuit for encrypting an identifier and a link communicative coupling the pad and the circuit adjacent in an access-resistant housing. An identifier is entered on the pad and communicated to the encrypting [circuit](/source/Electronic_circuit). The encrypting circuit encrypts the identifier. The encrypted identifier may be forwarded for [verification](/source/Authentication).

## References

1. ["EPP Security Requirements"](https://www.pcisecuritystandards.org/documents/epp_security_requirements.pdf) (PDF). Payment Card Industry. January 2009. Retrieved 5 April 2022.

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Adapted from the Wikipedia article [Encrypting PIN pad](https://en.wikipedia.org/wiki/Encrypting_PIN_pad) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Encrypting_PIN_pad?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.