A tamper-resistant or tamper-evident keypad device for use in secure transactions. The keypad comprises multiple security mechanisms to prevent tampering to the device, and thus access to users' private information. The keypad is made of resilient materials and contains a tamper-resistant collar for housing the keypad's connector interface. The keypad comprises a multi-layered printed circuit board with at least two internal security-shield layers comprising switch trace protection, as well as additional security layers for tamper protection. The keypad comprises a silicon-rubber keypad actuator that engages tamper switches on the flexible security circuit. The keypad comprises metal discs mounted on the front or rear face of the flexible circuit and an optional dome layer.

A circuit board is protected by being enclosed in a security housing that includes conductive tamper traces running along its interior surface, the conductive tamper traces being a housing portion of a tamper detection circuit. The tamper detection circuit also includes a board portion that detect tampering with the tamper detection circuit by monitoring voltages at monitor nodes along the board portion. The board portion of the tamper detection circuit is connected to the tamper traces via multiple connector pieces. The connector pieces can be held in place by board connector piece holders affixed to the board or housing connector piece holders of the housing. When tampering is detected, it can be localized based on voltages measured at multiple recesses along the housing. The tamper detection circuit can be arranged in a wheatstone bridge layout for environmental tolerance. The circuit board's functions/components can be disabled if tampering is detected.